I really wanted to like the new Apple desktop keyboards (specifically the one without the numpad because I actually like the minimalist layout, and want to reduce the distance to the mouse), but it just didn't feel good to me (not enough key travel). The new notebook keyboards on the other hand feel good; not as good as pre-unibody, but pretty close (I use both a unibody and an early-2008 MBP).
I haven't used one of these thin keyboards for a significant length of time (just tried it in the store for about a half hour), though, so I'm wondering if it's something that takes a little time to appreciate.
I use a Model M on the desktop, but I actually heard of someone who liked the Model M switching to the thin Apple keyboard because they liked it even better.
The Apple keyboard is very fast. Less distance to push keys down means more keystrokes in less time. On the other hand, I find it harder to hit the keys dead center.
I probably wouldn't go back, but there's room for improvement.