Wireless keyboards for HTPC seem to be a love or hate proposition, with most trending toward "hate".
I've been using a generic RF wireless keyboard + "nub" pointer for a while that was just … OK. I decided to research this again and see if there are any new wireless keyboard/mouse combos there for a HTPC that people tend to recommend with (almost) no reservations.
Surprisingly, the Iogear GKM561R keyboard + trackball combo seems to come out on top. It's the only one I can find that seems practical and has almost unanimously positive reviews.

Just ordered, but once I get it, I'll be sure to post impressions.
review: wow, I can totally back up all the positive reviews of this thing! I plugged it in and it "just worked" with no syncing. The sides have mild rubberized grippy edges which you can't see in the picture unless you squint, but is a very nice touch. And oh my god having an actual scroll wheel is like mana from heaven! I had no idea how much I missed a scroll wheel (and it's even clickable for middle click)! The optical trackball works great.. and being able to set the sensitivity, in hardware, of the optical trackball is a nice touch as well. Overall, this is easily the best of the 5 different models I've tried for HTPC integrated keyboard/mouse duties to date, and I can recommend it without reservation. Compact, smartly designed, and it has all the core functions you'll need for a HTPC.