http://www.microsoft.com/hardware/mouseandkeyboard/productde...
I just like the feel of it, but normal keyboards feel like chunky Commodore 64s to me now.
http://elitekeyboards.com/products.php?sub=pfu_keyboards,hhk... and http://www.geekstuff4u.com/happy-hacking-keyboard-pro-2.html
I also use a Das Keyboard, a nice full-sized keyboard with a great build quality---but it is extremely noisy and I wouldn't recommend it for that reason only. There is a silent version, too. Knowing what I know now, I'd go for the quiet one. Funny thing, daskeyboard.com sells matching earplugs for this keyboard. You buy a set for yourself and for everyone who works in the same room as you.
I know I am not the only one here who has gotten a keyboard form Unicomp: http://pckeyboards.stores.yahoo.net/
In terms of prolonged usage: it takes some time to get used to, it really depends on what kind of feedback you want form the keys. Further reading [comparison of different mechanisms and the tactile feedback they give]: http://geekhack.org/showwiki.php?title=Mechanical+Switch+Key... [more force graphs]: http://geekhack.org/showwiki.php?title=Switch+reference&...
As a PC user and occasional twitch-gamer, I personally stick with plain 104-key USB keyboards from Dell or Microsoft (quiet you), since they're fairly cheap to replace at local thrift stores. If my keyboard happens to die by misadventure, I'd rather not drop another $60+ just so I can use my machine comfortably.
When it comes to notebooks, the answer for me is and has always been ThinkPad, though the MacBook Pro/PowerBook keyboards are pretty solid as well. Sadly, nobody seems to be donating any MacBooks to my cause... :{
Plus it's semi-waterproof (water drains right through it, as long as you don't dump enough in for it to rise above the key silos and get in the electronics) and it can take a beating like no other for those angry typing sessions.
It's a nice keyboard but very, very loud. I can see myself switching to an Apple Keyboard sometime soon.
Alas, I can't comment on which modern ThinkPads are best. I know for a fact that X40 and X60 lines are perfect. I've never used an X200 though. On the other hand, I've had a T400-something from work for a few months. That keyboard was worthless compared to my current X60.
Although a generic budget keyboard (about £10-£15 here in the UK) it's become really popular among PC gamers (the sort who wouldn't think twice about spending £90 on a special gaming keyboard), and personally I've used it as my primary keyboard for years, it's never let me down yet.
Good feel, small foot print, and an old style key board layout that keeps Esc within reach of the home row for Vi-ers