Apple Wireless Keyboard
We'd just moved to a new office, thus a new desk, and for the first time in ages I found myself uncomfortable when typing. For years now I've worked directly on the laptop screen and keyboard, resisting the urge to hang external keyboards and screens off it. It's a laptop, it moves around, and I've always preferred to have the same environment everywhere, rather than having one screen/keyboard at work, and something different at home.
Also, I've always hated external keyboards. After typing on nothing but laptops for five years, I've become used to tiny amounts of key travel and no clickiness. I've lost the ability to press a real keyboard key all the way down, so my typing goes completely broken as soon as I try one.
The back pain dictated a change in this policy. So now the laptop sits on a pile of books, to elevate it to a sensible height, and the keyboard sits under it. Getting the Apple keyboard solved both my problems. It's a disconnected Macbook keyboard - exactly the same layout as my real keyboard, so I don't get upsetting layout changes, and the keys are laptop keys, so are easy to push and don't travel very far. It's the same width as my normal keyboard. Also, no wires. This is great in the same way that a wireless mouse is great.
The biggest surprise has been the new F-key positions. The volume controls have moved from F3/4/5 to F10/11/12, leaving space for Exposé keys, and naturally the backlight keys are missing. I thought this would annoy me, but actually the volume keys are now in much better places, and I get annoyed at the real laptop keyboard. I can find the volume keys without looking down now, by moving to the top-right of the keyboard, in the same way that I've always been able to get at the screen brightness keys by moving to the top-left. I don't use the media control keys, though. I have Synergy for that.
Recently it's going a little soggy, and I suspect battery failure. And the 'down' key needs pressing straight down to work, whereas I turn out to have been pressing the bottom edge of the key on the Macbook Pro. But these are trivial. I like it.