ive used both.

for me, i see 2 main benefits of the iphone. 1. if you own a mac, the iphone is nice to keep consistency with your mac(notes, appointment, phonebook, and other things to come). and 2, the awesome internet experience. if you havent tried, maximazing/minimizing web pages is pretty much instant and fluid.

but the n800 is also good in that you can install your own apps, tether and get 3g speeds, slightly larger screen(but lower resolution) and price.