Loading Linux on an iPaq is an afternoon\'s chore. It\'s not terribly difficult, but it takes some time. The screens aren\'t terribly much better than on the Zaurus. The post-3900 models may be a bit brighter, but the resolution is the same. New models aren\'t usually supported for at least a year, I think the 5xxx are the newest models are are currently compatible.
Cons: You lose the built-in keyboard which is a big drawback. You don\'t get the nice software on the Zaurus (especially Opera). You can\'t use CF cards unless you use a sleeve. You can\'t use SD slot for anything expect MMC cards (blame the SD consortium and their NDA policies)
Pros: You can use the sleeves, and some of the models have built-in wireless.
As a former user of ipaq Linux, I\'ve switched to the Zaurus, and I like it better. It\'s hard to use Linux without a real keyboard.
OTOH, the iPaq 4355 would be a nice Linux platform, but it won\'t be supported for a long time.