I get to start using my N900 tomorrow.

I'm figuring out which email clients are better/worse (will probably configure all) [use with gmail]

* IMAP -- The N900's doesn;t support IMAP IDLE right. Annoying omission really. IMAP IDLE is perfect for these devices!
* nokia messaging - Had bad experiences with reliability on S60. Hopefully maemo better. Formatting was the best though
* Exchange sync - I used this with google on S60 and whilst simpler, it was very reliable