I prefer the Microsoft natural ergonomic 4000. Its a lot easier on my wrists then any of the straight keyboards. I haven't seen any companies that offer a good competing product in the ergonomic style, though I may have just not looked hard enough.
Also, I don't like wireless. Beyond all the hastles of wireless, batteries, etc, they are an open invitation to people who want to know what you're typing. Worse, they can allow hackers to get into you computer, steal information, identities, know everyplace you wander, and other bad news.