I like the N810, I've using one for ages.. but it's a bit of a dead fish.. The N900 is the next evolutionary step.

I wouldn't buy an N810 now because a) there's no more Nokia development and b) it's not a phone.. but it doesn't stop it being a great device!

The n900 is muuuch faster though.. the email client is fantastic (speed wise) compared to the n810.. and the browser is pretty fab too!