I like it. And it doesn't seem to be all that expensive when compared to other Modular helmets. I think anything that increases a riders field of view is great.
I can see this one situation where this thing would beat side mirrors all to hell. Sitting at a red light. Whereas you might not be looking at your mirrors, you just might notice something coming at you a little to hot from behind with this thing on.
I'd be curious to see what effect it creates at night with headlights behind you. I can see that actually being a problem.