@robiski - Sorry for the trouble. Software is close and should be available in a couple weeks.
We are now in October. The 520 was not compatible out of the box (contrary to advertisements) and in the first week of September Garmin stated "a couple of weeks." Garmin you will shortly be getting a request for a full refund. In concept the idea was grand, but the product has failed to deliver.
I am glad that Garmin is at least now pointing out that the 520 is not yet compatible with the Varia. Would have been nice if they gave the early adopters a heads up.
Today Garmin released a firmware update for the Edge 520, which not only seemed to fix a number of bugs, but also added Varia support. My Varia radar is now connected with the Edge, and no longer a paper weight!
Added support for Varia Smart Bike Lights. Now you can form a network of lights including head lights, tail lights, and a rearview radar tail light.
Added support for sensor software updates
Added the ability to edit crank length for PowerTap P1 pedals
Added dynamic zooming while displaying the elevation graph during an activity
Added a Percent Effort option for adjusting the virtual partner speed when following a course
Added a preview of an incoming text to smart notifications
Updated the FTP test to include setting a goal and accepting or declining the test results
Fixed an issue preventing accurate data from being displayed with an HRM-Run
Fixed an issue preventing the elevation graph from being drawn correctly
Fixed an issue where segments would randomly not start
Fixed an issue where courses would sometimes not start at a point along the course but away from the start location
Improved device performance with many segments loaded
Improved device performance while navigating through the list of courses
Improved stability of device-to-device transfers
Various fixes for general improvements to stability and performance
First the positives; I was impressed. Audio alert when a car was picked up (car back!) and a visual alert of the 520 - yellow bars on the side. What I was not expecting is that the 520 also has on the right side a car indicator. The cars are represented by moving dots that reflect the approximate position of the vehicle(s). So you can glance down and see the number and approximate position of the vehicles behind you. Since I was commuting I noted that Varia picked up at least three traffic lanes (cars in lanes #1-3 were detected) at least 100 + meters back. While I was stopped at a traffic light I watched it detect and display multiple vehicle positions. Looking forward to its use on low traffic rural roads to catch my attention if a car appears that I did not notice - so I am now a big fan.
Negative; the 520 Varia display stopped working 35 minutes into the ride. Since i was commuting I did not trouble shoot this issue. The 520 continued to work and the Varia appeared to work - just no Varia display on the 520. Perhaps the link was dropped.
It will be interesting to see what the impact will have on the 520 battery life. For a 50 minute commute it rocks; for a century or a double century we will have to see.
Even with the dropped connection I am willing to continue to be the beta test for the Vaira. When it works it is far better then I expected and it is an extra set of eyes that yells "car back" (or beep). That by itself is worth the price.