What I like about the chicony is that it has an integrated touchpad below the cursor keys that comes handy when I'm suffering from mouse elbow, which I occasionally do.
I don't miss the 3Dness of the Microsoft keyboard (which I have at work). Note that I have the original Natural model there. Their current models both kinda suck - the "Elite" version has tiny little cursor keys and an extremely stupid layout of the Del-Home-Ins-End-PgUp-PgDn block, and the "Pro" version has lots of useless bells and whistles. The Chicony board has a very good tactile response to pressing a key, and is quieter than _my_ MS board. The newer MS boards have a much cheaper feel to their keypresses - in essential, the current MS board has the looks but not the guts.
On either, I currently notice that I'm increasingly pissed off by the unnatural way the fingers of the left hand have to bend because of the stupidly staggered rows of keys (that actually stem from the mechanical requirements of the original typewriters of over 100 years ago). And as a programmer, having to type the {[]} brackets on a German keyboard is annoying too.
So I'm currently trying to get hold of one of these
http://www.darwinkeyboards.com/smart_core.htm
but it seems they're not very interested in actually selling their stuff ...
regards, Peter