Ive been using mine for about six months on my daily commute, together with the Garmin UT800 front light. A truly great light/commuting combination and would recommend either of them. That said, there are things that you need to be mindful of with the radar/light.
It is fool proof and certainly doesn't take away the need to do a quick sanity check over your shoulder before turning. If a vehicle has been behind you for a few minutes, then the "icon" will disappear from your screen and only appear again the when car is level with you as it overtakes. Cars coming out of side roads or islands will not always show either, as the unit needs a decent distance for the beam to detect a moving vehicle.
Another thing I noticed last week when I used the radar/light for a ride out rather than my usual 1.5 hour round trip commute, it certainly gives the battery a hammering in the GPS unit, in my case a Edge 500. My ride was around 3.5 hours and 60 miles, and it took the battery level in the GPS from being 100% charged down to less than 10%. Normally I can do a 100 mile ride and still have more battery percentage left than that?
I also dont particularly like the Garmin Universal OE mount for the seat post that is included in the box either, its very easy to catch with your legs and knock the unit out of the best alignment. Would certainly recommend getting the much better Garmin, specific seat post mount, its a proper Nylon hinged bracket and holds the unit a whole lot more secure. But the downside, its another £14 odd quid to factor in to the overall cost.
But minor niggles, I still miss it when I go out and dont have it fitted to the bike, and recommend it to you if you commute, but maybe not as an everyday device though?