One thing I'd really like is MAME emulation, but I'll be using it for:

multiple messenger services (will MSN and Yahoo messengers be available?),
IRC (is that available?)
skype,
emails,
taking photos (I don't have a "proper" camera),
listening to music/podcasts,
Games/emulation
it'll probably be my main browsing device,
showing off n900 multitasking goodness to Apple zealots...!
Making phone calls. I get 3000 off peak minutes