Not sure about email as I use the default "Email" app on the N900.. I use Sygic for navigation (Ovi Maps serves as map only no turn by turn navi).. there are many applications like xplore but the only problem is that it's not user friendly like xplore.. but it's really not that bad... gmail app, well I use the Email app or the browser which is super fast.. once you use MicroB you will never would want to go back to opera.. live messenger, you can use the MSN Messenger plugin which will work on conversations and contacts... skype is built in with the N900.. Calendar is just like the Calendar in Symbian.. and finally there's a weather app, 2 of them actually so I am pretty sure you will like the N900...

I went from N95 to N900 and I don't regret it at all.. My advice is to try the N900 and dig deep into it.. find every cool thing about it.. SEARCH maemo for cool tricks/hints/apps.. etc..