I looked for a long time for a keyboard that would be perfect for use on my HTPC. After looking at a lot of what was available a few years ago when I built it, and reading a lot of reviews, I ended up buying a Logitech Mediaboard Pro http://www.logitech.com/index.cfm/keybo ... 6&cl=us,en
This thing is designed for use with the PS3, and uses Bluetooth, but I find it works with Windows XP Pro fine, with an off-the-shelf Bluetooth dongle.
The only problem with Bluetooth (at least the way it's done with any dongle I've tried) is that the software on the computer with the Bluetooth dongle/card seems to need to have a true Bluetooth stack to interpret the keypresses. This means that typing a key on the keyboard won't start a machine that's sleeping, and no BIOS or other software without a Bluetooth stack can read the keypresses.
Also, though I don't usually like Trackpads (eg. I only buy Thinkpads for laptops, partly because I like the "Trackpoint" mouse in the keyboard better), this one works better and feels more accurate than the trackballs I've seen on some other keyboards. Also, some Adesso keyboards with Trackpads I've tried were not very accurate and seemed to lose the connection rather often.
It's a little wide, but I've found the batteries last a really long time, the mouse and typing accuracy are great, and it's made to live in a gaming environment where it can get knocked around and spilled on (tho' I haven't experimented with that part
Also, some people have reported they hated the key-feel, since there's not much travel in the keys; they've reported finding they feel like old-fashioned calculator keys, but I haven't felt that at all.
What I'd REALLY like would be a Thinkpad keyboard like the below, but with Bluetooth: