I bought the low-end Sony Clie SL10, and use it to carry around an electronic version of the address book we use - my wife still prefers her paper DayTimer-type thing, but this is good for trips. At the time, this was the cheapest PalmOS PDA I could get, it uses AAA batteries, and as long as you stay on top of the battery level it's "good enough" for what I use it for. I don't carry it every day, and I don't run my work life via PDA, etcetera, so I don't need the latest-and-greatest. The Palm Desktop software is "good enough" too, pretty much - it handles the address book and the calendar in a Windows environment; I can HotSync the PDA to the Desktop on both of our PCs over our network and it works OK. The only quibble I have is the lack of import capability for iCalendar files, which is a "nice to have" not "have to have" feature.
I _have_ been thinking of downgrading, to an "organizer", which would have longer battery life, but I'm not sure the display is adequate and I'm unsure of how we'd synchronize and what we'd synchronize to. If you've experience with one that connects to a PC with Windows, let me know what you think.