i too spent several months trying to decide which device i liked better. For me the fact that the n800 supports BT dun, skype, and is more like a pda where the touch is more amusic player with a marginal browser. the n800 will blow the touch away with its full power browser, while the touch is really only for light surfing. battery life is comparable, video is better on the touch. os2008 works quite well on the n800.
So like someone else said ... if media and flashy are most important then touch is a better choice. If you want a full browser with dun then n800.
other points n800, speakers are actually pretty handy, its smaller than it looks, there is a big input window so you can use your fingers, not quite as easy or fast to type on as the touch without a bt keyboard, in my opiniin they need to be combined and they would make a sweet product.
i have used some nokia phones, the n800 feels like your using a nicely polished kubuntu release or something. I am quite pleased with the functiinality of the n800, so much so that i dont own the touch anymore .... i do have a new ipod nano that will fill the gap for now. I am excited to see what these will evolve into.
Anyways, if the touch doesnt quite cut it, dont be afraid to try the n800, i know i prefer it. btw i wrote this on my n800 lol
afterthought ... flash cards are easy to change ... for some reason people are really hard on the n800, i like apple stuff as much as the next guy, but the n800 is a really nice peice of kit too! just aimed at slightly different markets, both excellent products.