Is there actually a difference? I may be a bit confused, but it all looks like part of the same global 'google account' to me. I mean, I log in to gmail, then I can either mail or chat with anyone in the contacts list. I found out by accident that everyone I had set to 'always in quick contacts' would be automatically imported to my N800 as soon as I went online. Some of them I had been chatting with in the past, others I had only used for email. In any case I can now either email or chat with them from the N800 (or they can chat or email with me, on the N800).

In the Contacts list on the N800 the gmail accounts do appear as 'Google Talk' contacts, but they're still from my gmail contacts list.. and can be used for anything on the N800, e.g. email or google talk.

EDIT: p.s. All the gmail contacts I'm mentioning above are other gmail accounts, I have not checked if the N800 can import non-gmail contacts.