I have the 2200mAh extended battery and am quite pleased with it. I don't run out of power even on a very heavy usage day. I prefer this to carrying an extra standard battery. The extended battery does add a very noticeable bulge to the back of the Axim, but it doesn't bother me a whole bunch and, to me, its worth the extra up time.
Soooooo....you've got three replies so far, with three different opinions

And you'll soon realize that's the way it is with most decisions about the Axim. It's a very personal device that you can customize to your specific liking. There's rarely a
right choice; it all boils down to what you prefer and what works best for you.