It's a PDA, except it's got a big harddrive (3.6 GB), can act as a USB host and has a full keyboard. It's almost a mini-laptop! The screen is lovely (I'm spoilt by Sharp screens) and the keyboard's actually quite nice to type on. The on-screen keyboard isn't great - because the screen is very smooth and offset about a millimetre into the screen it can be a bit tricky to hit the correct spot on the keyboard.
I got myself a 802.11b wireless LAN card (which was my first foray into Ebay buying), and it works really well. Even running the wireless card I can get about an hour and a half out of the battery, and without the wireless and running the backlight quite dark I can get 3 or 4 hours of continuous use.
One of the features I've been using most is the infra-red port, to talk to my phone. I use the camera on the phone to take pictures (like the ones you see here), and then transfer them onto my Zaurus as a stopping point on the way to my PC. I use the excellent ports of KOrganizer and KAddressBook to the Zaurus to manage my todo list, schedule and contacts, and with the infra-red I can also use them to update the contacts list on my phone -- very useful, as it means I only need to type contact details into one place.
Unfortunately, I am having more than a little trouble with building software on the Zaurus: I think it's something to do with the library search path, but I haven't been able to crack it yet. I did manage to get Emacs to build, but I've been plagued by keymap difficulties.
On the whole, though, I'm very impressed with the Zaurus -- it's just a real shame that Sharp have decided not to release it in the UK. I had to mail order it from Japan, which was quite expensive.