The rearview radar works as promised - I noticed cars giving me a wider berth on the road and I felt more aware/alert as well.
So, five stars for function, but I have 2 complaints about design and use:
-there's a tremendous lack of guidance/instruction. It seems everybody wants to be Apple and ship their product with just a single page instruction paper that makes you feel as if the design is perfect and easily intuitive. Much more is needed here beyond the thin "here's your on/off switch" basic instructions. Set-up and integration with Garmin apps IS NOT intuitive (but you can figure it out - its not impossible) and initial useage was hit or miss until I figured everything out. My problems were magnified because I was trying to connect the Varia to my Garmin watch (Vivoactive HR). There's almost zero support for pairing a Garmin radar with a Garmin watch, even though this is promoted in the marketing material
-after plunking down serious coin for the radar, I was shocked to find that the recommended way to mount this on my bike was using a rubber band! There's a mounting bracket included, but it's for really thin seat posts - mine was too big, so I used the rubber band mount. I'm very worried that my significant financial investment is going to snap-off mid-ride. (Though there's been no indication of this after 250 miles of pedaling.) Garmin, please invest a bit more in a seat mount for fatter seat posts!
So, 5 stars for function, 2 stars for support. This product can save a life, though, so the set-up challenge is ultimately worth it.