Regarding sales of Pocket PC/Palm units...around our company, we've completely stopped using them. It's all Blackberry's or Treo's. In my unscientific polling, most people I've spoken with consider them approaching obsolesence. In my personal opinion, they fail the pocket test--sure they're called "Pocket PC's", but what pocket? The huge cargo pants' pockets, maybe. Not a standard shirt pocket--especially with the cases.
I agree with philhedge in that if I need near-full computing power, I'll lug a laptop, otherwise, the device had better fit very nicely into a shirt pocket. I think the problem with pocket PC's is the form-factor--too big to truly be 'pocket-sized', and not enough power/useability to warrent lugging them along. But yes, there are a few uses where the tradeoffs of slightly larger size but slightly more fuctionality than a Blackberry gives them relevance.
That's just my opinion, I could be wrong
--Jim