my personal use of a N800 would be:

1. early morning web browsing (usually odb plus fb) while making breakfast.
2. check weather before leaving home
3. mails for quick view when i am not on desk
4. quite some FB (and Twitter via Mauku)
5. quite a lot of Sodoku using Simsu
6. taking notes using Maemopad+
7. sometimes i use it to prepare my shopping list via Todledo, just load it up when i have WiFi, then off i go to shopping
8. i write scripts on it, and play with the programming part of it (PyMaemo)
9. i use it to VoIP - the built in client works pretty well with SipGate.
10. i do use the alarm clock on and off. the third tone is pretty nice
11. i do use MaemoMapper on and off. but usually i don need that (have no car, you see... :P)

I believe you can do quite a lot on it, and a N810 at this point is perhaps a very good priced device. have fun!