I picked up a cheap n800 - GBP130 - via a friend of my brother in california
I love the n800, but it's a very different beast to the zaurus and my palmt3, and all are different from my sony tx2 ultraportable.
I use the zaurus as a mini linux laptop for actual linux experimentation - coding, shell scripting, serial terminal, wireless sniffer, etc. I've learned a bit of qt/qtopia and wrote a simple game. It's currently being my android playground, and I hope I can dual-boot cacko with angstrom/debian/android at some point!
I use the n800 as a web browser, media player, radio streamer, occasional email client, mapping, and basically any interesting application I find - it's more of an appliance to me. perhaps it's the lack of a keyboard? I have been trying to get scratchbox installed, but it's not been trivial, as I want to be able to compile stuff and learn a bit of hildon/maemo/gtk.
I use the PalmT3 solely as a PIM, at which it is excellent, and for some palm games, and occasionally to run TomTomPalm. The screen res is too low for browsing, and it doesn't have wifi anyway.
If I had lots and lots of money and didn't care about the waste, I'd ebay the lot and probably get a PalmTX* or Treo for PIM and games, and a Nokia N810 as my handheld linux hacking tool. For a laptop I'd probably get the Toshiba R500 - have compared them with my Sony TX2 and a colleague's Soiny TZ and they're a bit better; I might consider the Fujitsu U810 but I suspect the keyboard would be frustrating.
* I bought my wife a TX for birthday, and I like it quite a lot. I should have given her my Palm T3 and kept the TX!!
this is all my personal perspective, and all these devices have compromises that some people don't care or don't notice, but other people cannot stand!