I actually went from a Palm (Sony Clie TG-50) to the 3100 (I had used Zauri before, but not the Linux variety). I wrote
a review of the 3100 for The Gadgeteer which might be a good overview, but let me compare it specifically with the Palm.
The Zaurus requires a heck of a lot more tinkering to get some things to work (specifically, things that aren't supported by Sharp out of the box, like bluetooth). The Palm in general is a lot easier to set up and use, but it can also be less flexible. It's great to be able to use a wide range of USB peripherals with the Zaurus, for example, but in many cases it requires a fair amount of command-line tinkering to get them to work. If you don't like manually editing text files to configure programs, you probably won't like trying to get the most out of the Zaurus.
The keyboard is much better than other PDA's keyboards. The TG-50's thumboard is a total piece of crap by comparison. Same goes for the screen.
The amount of software available for the Zaurus just can't be compared to the Palm software library, and (to a non linux user, at least) a lot of it is rather hard to install and configure. The PIM software included with the Zaurus pretty much sucks, and I don't think any of the other software packages available approach what is available for the Palm in terms of ease of use.
You have very basic office compatibility with the built-in apps, but you might want to look into buying TextMaker if you want a really robust word processor. There are also some free alternatives like AbiWord and Open Office, but both of these require the XQt environment and don't run very fast in my experience. I don't think the Zaurus has anything like Documents-To-Go or other Palm apps that can actually sync Office apps.
The web browsing experience is a lot better on the Zaurus, once you get it set up. The included browser is ok, but Opera is better in my opinion. But again, installing Opera is a little tricky.
I like my Zaurus, but I am hesitant to recommend it to people unless they realize that it's a bit more labor-intensive than a traditional PDA.