imho, it depends on the user...
some people love the ergos...i hate'em hehe
I could never get used to the one we got...my typing was like waaayy slow

Like <40wpm...my speed on a regular keyboard is 90-100wpm hehehe And it just felt really weird to use it...so i went back to my trusty Dell QuietKey (i love this thing)
It really depends on how long you've been typing/how profficient you are with typing, etc
Personally, I found that adding a keyboard tray really helped- I can type/play games etc for hours on end w/o feeling anything. (My desk is a bit too high...if i sat at the comp and typed/played for over 1-2 hours...my shoulders got really sore

)
just my .02,
-eric