I’m on my third or forth year with my 820. Bought it when they first came out as the bundle package. Overall I am very satisfied with my purchase. There was a software update that was a dog but the next update seemed to fix everything. All the advertised features work on mine but I only use the heart rate, cadence, speed , di2 gear and di battery check. And of course the map/route upload to Garmin connect and then Strava. I have uploaded a turn by turn route file a couple of times and everything worked well. Strava live segments also works well but I prefer not to use it. I do have some screen halo but it’s not enough at this time for me to send it in for replacement. I have found it is important to have Garmin connect open and running in the background on my phone for a seamless post ride upload. Di2 integration is very important to me and it works very well. Internet WiFi and phone Bluetooth work well and are pretty seamless.
There are quite a few choices available now that were not around around when I made my purchase but I think I would make the 820 or 830 choice again. I like the size and features that are important to me. As long as the Garmin software people do not mess it up, I believe the 820 Will continue to work for me.