I have an IPAQ 6340 which has wireless, bluetooth and is also a 3G phone so you can slip any simcard (2G or 3G) into it and away you go. I also brought a bluetooth foldable keyboard which is outstanding and much better than trying to use the stylus or the tiny keyboard that comes with the IPAQ.
I learnt to my cost that you just can't beat a laptop if you need to read something with a decent screen size or do some spreadsheeting or prepare long word documents. But for receiving and sending emails on the go and perhaps viewing the odd document it is fine but you definately don't want to try and sit there for hours on end using the cut down versions of excel or word as it is just to frustrating and time consuming.