I recently received my N900 (it had to be forwarded on to me in Australia from the UK) - and it's easily the best phone i have ever used. Maemo 5 rocks, and its amazing to be running this kind of software on a device like this.
The web browser is fantastic (based on the gecko backend) - I've composed all of this post on the device using the standard wordpress backend.
Seems to work fine with Ubuntu as well - it shows up as a mass storage device and a GSM connection when I connected it to my machine with USB.
I have been attempting to improve my python skills, so maybe I'll attempt to create some simple python and gtk apps.