Currently still using my trusty old Casio E-125 every single day, and it works just fine. A bit on the heavy side, but solid... it has had a couple unfortunate run-ins with the floor so far and no problems whatsoever.
I'm about to trade up to the new Fujitsu-Siemens Pocket LOOX (I didn't name it
) though, with the phone addon. Always-on network access and phone functions in one box, with the new Intel XScale 400mhz cpu in it too... woohoo.
Don't have any Xscale sites offhand, but it's essentially a Strongarm CPU (100% compatible) but with much improved power management. It scales CPU power up and down depending on load... maybe that's where they found the name, who knows.
If 400MHz is required it goes to that speed, but when idle it slows down.
At least that is what I have picked up via the net. Doesn't have to be 100% accurate.
The new Fujitsu-Siemens is supposedly going to have a minimum of 12 hours of non-stop usage time out of the box, which is pretty darn good. With occasional usage (like most people do, much less than 12 hours a day) it should last days between recharges.