15/20 SECONDS GRADIENT LAG. TEMPERATURE DISPLAYING 2/4 C DEGREES HIGHER

No. All Garmin's have these faults. There is always a lag in reporting gradient, current elevation and total ascent in the various Garmin devices that I've used. Temperature is always inaccurate as the internal temp sensor is heated by the active internal circuitry and external solar heating of the device.

I agree that the Sony GPS is a POS. My old 810 tracks GPS much better than the 830. 

I have read in 1030 forum that GARMIN Edge 1030 haven't these problems. Gradient is only a basic algorithm in fact is only a simple calculate between distance earned altitude and distance ride. This must be very very easy to fix for a basic programmer.

And temperature is a hardware problem yes, but not for sun because temperature go up inside home, you only have to turn on screen and you can see at the beginning correct temperature but in two minutes you can see how temperature go up 3/4 °C . It would be very easy too put sensor insolated but if it were very difficult to think  for GARMIN team,  they can also fix this problem with software .

With support for varia radar on other GPS units and the disappointing experience I have with this unit (together with others in Garmin lineup previously - 510, 520, 1000) I believe this is indeed my last Garmin device. Today it disconnected all sensors three times. Awful support from brand, better support in this forums, but I've had it. When time to upgrade I'll look somewhere else.

Its a shame since a new costumer is much harder to get than a current one...

I wouldn't dare to say "easy to fix via software". If you're using a map/course which includes altitude data or if the barometric altitude sensor is very reliable, you could indeed indicate the actual gradient instantaneously provided that the GPS positioning data are correct. Several contributions in this forum have however made it clear that the GPS chipset in the 830 (i.e. the hardware) is not providing stable, correct positioning data. So the only way out of that is to smooth these "faulty" positions out by taking averages (software) over a relative long distance/time. Hence the lag. Reducing the averaging distance (i.e. smaller lag) will simply lead to irrealistic numbers jumping up and down. Also if your bike is equipped with a speed/distance sensor there is still the need for the exact GPS position, as some may ride uphil zigzagging, others straight, which the software cannot know. So no easy software fix that will work in all circumstances.

For using the internal temperature sensor as an indicator of the external temperature - i.e. to "correct" the temperature via software - you'd need to know several external factors: if the sun is shining, how the edge is mounted, if there is wind, and yes, also what the external temperature is (because the difference internal-extenal will most likely depend on the absolute external temperature, i.e. it won't be a constant number), etc.

So more a hardware issue than a software one, I'm convinced ...

Certainly the arguments you give are very reasonable. Surely you are very close to reality. I had read something about the imprecision of the new Sony chipsets and had it in mind, but these arguments hit my head because I had also read arguments in favor of this new Sony chip that it was more sensitive and accurate than the most ancient. I initially thought that inexperience with this new Sony chip was going to give somewhat mediocre results due to GARMIN's nefarious habit of launching their new devices unfinished and using buyers as testating helpers to GARMIN engineers, but that after a short time they were going to be able to get the Sony chip to work better than the previous one.

I think I was in a mistake, and surely this Sony chip is to blame for these new GARMIN EDGE 530/830/1030 plus being so inaccurate.

After reading you then I wonder, is it worth having one of the 530/830/1030 plus devices? They are very pretty and glamorous but GARMIN should put a big label accompanying their sale:

"ATTENTION DEVICES WITH BETTER BATTERY AUTONOMY BUT WITH MANY JOKE, TOY, FUNCTIONALITIES.

PURCHASE AT YOUR OWN  RESPONSIBILITY.

I'm still waiting for a response from GARMIN. I'll keep asking until GARMINN confirms it for me. Then I'll demand my money back and buy an old edge 1000/1030

After 18 days waiting, GARMIN has responded. The only answer now is, that according to the information I give them, I have to send my device to their facilities.
Just this, not a single word about whether the bugs are common or not, whether they are fixing it or not.
They also don't tell me if they are going to try to repair the device or send me a new one.
What would you do in my place?
Would you require a garmin commitment to pay me back? since from what is read in the forum, are general failures, with which the new one that they send me will be just as bad. or even worse, send me one repaired with the same faults and on top of that it would no longer be new and with a shortened warranty.

Still waiting any informtaion of these problems . Garmin any answer?

15/20 seconds lag on gradient sounds reasonable to me.  You need to get a measure a horizontal and vertical distance to work out the gradient.  If the distance between the measurement points is too small then any measurement errors will be amplified.

If you want instantaneous accurate gradient measurement you will need to spend a lot more money on a device that can perform the required measurements.  Expecting such things from a consumer level device is expecting a bit too much really.  How much does the general user base really need this info?  I don't know but it isn't everyone.

Most people will really only care about having the speed/distance/tracking/HR recording/power recording accurate enough and the Garmin units do that just fine.  If they use it for navigation then those features working properly is also a must.

I think you are really over estimating the accuracy of consumer level GPS systems and simple pressure sensors.

Temperature 2-4° above the air temperature sounds reasonable too.  The temperature sensor measures the temperature somewhere inside the unit.  The unit being active will generate heat so it can easily report a temperature a little higher than the air temp.  The temperature sensor won't be really calibrated either.  You will need to pay more for that to happen.

Is a temperature a couple of degrees above the air temp (how are you measuring that by the way?  Is your source accurate?) really a big issue?  Why do you need it to be spot on?  I would suspect it is a metric that most users don't really care about very much as it isn't a metric associated to any cycling effort.

BTW the GPS chipset has nothing to do with pressure or temperature readings.

• First and foremost of all. If GARMIN is not able to give precise measurements of any specific data due to material disability or development disability, the first thing that GARMIN should do is not to put this data on the device and not to sell it as characteristics of the device. If what GARMIN wants is to sell it as toy functionalities, as a joke funcionalities, that GARMIN clarifies it with capital letters on the box and in all its manuals, something like: "MOST OF THE FUNCTIONALITIES OF THE DEVICE ARE A JOKE, A TOY, THEY ARE NOT ACCURATE . BEFORE BUYING ONE OF THE MOST EXPENSIVE DEVICE ON THE MARKET YOU HAVE TO BE AWARE OF THIS AND BUY AT YOUR OWN RISK AND LIABILITY. GARMIN IS NOT RESPONSIBLE FOR THE RELIABILITY OF THE DATA. "
• Speaking of gradient delay, 15/20 seconds is a long time, even much more lag than GARMIN EDGE 1030/1000/520 devices. The temperature I have contrasted with other devices for example EDGE 520 and 1030. I have also contrasted it with two weather stations that I have at home. By the way these functions are very important (different thing is, that you do not give importance). Temperature,to know when there may be ice on the road, to know if an overexertion in summer may be due to physical exercise or heat because it is not the same to climb a first category port with 30 degrees Celsius than with 40 and when you are pedaling to the limit it is difficult to differentiate these things. Another function that Garmin itself brings is that of "acclimatization to altitude" in which the temperature is decisive.   A very accurate temperature sensor is very cheap and tiny, and they are accurate even in terms of 3 digits after the comma, not that much is necessary but properly isolating the sensor would suffice. Gradient Percentage, It is important to be able to train and adapt the development of the transmission to the slope of the road, to be able to dose well the forces in long distance routes. It is not worth that they are unimportant functions, if we are strict on the device itself it is not necessary and it is not necessary to spend $ 600 on a GPS. All the data they give is superfluous, even there are paper maps and with a pencil and a book all the data are taken when you get home sitting after a shower. This argument is stupid on its own.

All consumer GPS units will have a horizontal accuracy of about 5 metres.  This is perfectly good enough for these type of devices.  If you want more than that you will be buying more specialised equipment.

Vertical accuracy of GPS is less due to how it works.

A temperature sensor may have good accuracy (Note that precision, amount numbers after decimal point, does not mean the same thing) but when combined into a device not designed for highly accurate air temperature then the end result will be not quite as accurate.  If you can design and build a better device for the money go for it.

If you know the temperature is close to freezing from your weather station why do you need you Garmin to also tell you that?  Your Garmin will tell you it is cold and if you know the temperature reading is a little higher than the actual number just compensate in your head.

You just really need to lower your expectations to reality.  You won't get any better results from any other similar device on the market.