Ok so I bought an iPod touch 8g (2nd gen) and have been an owner of N800 for about 1 year too. I am no apple fanboy and use Ubuntu as my primary OS (with Vista as second). Heres my unbiased opinion :

a) iPod touch is a good Mp3 player. The sound quality is way better than the N800 especially with good earbuds (not the bundled crap). Its still not the best sounding player but its still pretty good. The battery life when playing audio only is also much better than the N800.

b) iPod touch does not do skype though I am now told that finally apple is selling a mic+headphone for the touch for $30 and that it will enable me to use skype via fring. But this is untested and so currently N800 is a lot better at VoIP particularly since it comes with mic inbuilt and decent skype support.

c) Mail, Facebook : The mail app on the touch was very easy to setup, works consistently and is pretty responsive. The N800 mail apps have been very lackluster and I always had problems with most of them. On the N800 I just use some webmail interface.
The Facebook app on the touch is also pretty awesome. I dont think anything comparable exists on the N800.

d) Chat : No background apps on the touch and hence chat is lame. N800 wins this one.

e) Browser : I actually dont use the browser that frequently but the speed of both browsers seemed adequate for the types of site I browse. However I do prefer the larger screen of the N800 for browsing so N800 wins this round.

f) On screen keyboard : The keyboard on the touch seems to be in the portrait mode which basically means a very small keyboard. The on screen keyboard on N800 is much better and has better precision when using stylus. Thus N800 wins this round.

g) iTunes : I dont like it and the fact that I have to use iTunes to manage my iPod is rather lame. Thankfully though Apple has moved much of the management functionality to the device itself.

h) Boingo : I dont know whether its possible to use this service on the touch. I use it frequently on the N800.