Something like the 4150 is probably overkill for what is being talked about here, but I have one, and can say it's a very nice machine, indeed. And it's remarkably cool to put an Amiga into your shirt pocket. :-) So far, I've been quite happy with mine, despite some small annoyances associated with any device that flies that wavy 4-colored flag...
I know you said you were more concerned with function than spice... But if you have to carry a device like this around with you all the time... Why not have a little fun with while sitting in a waiting room or whatever? You can't beat the power of the newer XScale WinMobile2003 devices.
For boring uses, a PalmOS machine is probably a little cheaper, easier, and better on the batteries. But not by too much, anymore. The handwriting recognition on WinMobile has gotten a lot better. I haven't had a problem with battery life [unless running Wi-Fi], and I'm consistantly on the road for 12+ hour days when I'm out. Granted its not on solid for those 12+ hours, but I've have it on for probably 4-5 hours a day and rarely drop it below half-charge.
And versions are available with built-in keyboard (though you might want to try one at a store first - I have the small detachable keyboard for mine, and it is basically useless junk - I would hope the built-in keyboard would be much better.)
For pocket applications, PocketWord, PocketExcel, PocketOutlook are fine. The built-in contacts, tasks, calendar apps are fine, too. I use "SecureWord.Mobile" to track my many contract-related administrator accounts and passwords. It's been the best password-tracker of what I've found so far, and it's free. (As in beer, not GPL, but hey, good enough.) :-) I thought the built-in calculator app was crap, so I downloaded VTi and dumped the ROM from my old TI-85 graphing calculator to it. Now I can emulate my TI (faster than original speed) from a handheld device less than half it's size. :-)
So essentially, you can get a lot more from an XScale device, while giving up very little.
