I reviewed this and don't see how to update my review so doing this again after several weeks of use. This is a great item. I don't notice it when I don't mean to and when I do hear the beep notifying me of an oncoming car or notice the dots moving in the Varia Vision, I am as forewarned as is possible. For safety and the other information in it, it is excellent.
I bought this specifically to combine with the 820 and the Varia. The Garmin 820 has the beeper that works with the Varia to let you know of approaching cars, under the mounting area. It can barely be heard with the Garmin mounting bracket. (fortunately it can be heard decently with a 3rd party mount). The Varia Vision, aside from giving assorted data (I am not sure if those shown data fields are changeable but that would be nice) gives you better feedback of approaching traffic by putting it right in your face. A short amount of getting used to it and it works quite well. As for blocking your vision, it doesn't. I have mine in the upper right corner of my vision and unless i am focusing on it, my left eye sees the small area covered by the VV over my right eye. The mind and sight do this perfectly. It could be improved in many ways, but for my most important use, it works very well and especially when on sale, is well worth it. Safety always is.
I was curious how the eye focus would work out being so close to your eye, and it was perfect. Comfortable to focus on, even at that ultra close placement. It does have to be positioned just right though to be able to see all fields to the edges. I felt I had to share my experience as it was entirely different than the other existing review. The only difference is that I am using the Edge 1000. It paired without a hitch. I have it set to display 2 data pages of 4 fields each all of them are correct - and it is showing my radar display on the right edge as well. The only drawback is that the support structure does slightly block your vision when glancing to that side. But the only time I notice it is when approaching an intersection. And I don't feel it's that hard to compensate for. For me, this was one of those things that worked so well I don't even think about it anymore. I love it.