Did you have issues using a Microsoft 4000 keyboard with your Mac?
The only issues I had (on Lion) were with the Microsoft drivers not retaining their settings between reboots. It seems the drivers were vastly improved (no more kernel panics) since you've tried them; see David Röthlisberger's article.

Other than that, I think the ergonomic part is well worth the trouble of getting the 4000 set-up properly. And with KeyRemap4Macbook you can get almost limitless customizability.