Yes, I put the D606's on both the front and the rear. They seem OK to me. I didn't really have a problem with my trailwings, but I'd read that the D606s are much better ... plus I wanted as deep a knob as possible for studding (which I decided against later).
I can't really tell the difference on road ... except they are maybe a bit less smooth, and I have yet to take them off road (snow doesn't count).
My only "issue" with them has been the size, and consequently the need for the smaller front sprocket (I could have gotten a longer chain, but that cost more).
I **don't** like working on my bike, unlike most people (if i was better at it, I might like it, but as it is, I know just enough to break stuff), and ended up stripping a screw on the front sprocket when I swapped it out ... plus with the smaller front sprocket, the chain lies heavier on the chain guide, and I don't know if that is something I should worry about or not.
When the rear D606 wears enough, I'll probably put the original sprocket back in.
The future is wide open.