Open Source phones...lolz
Seriously, as an early adopter of Linux on a mobile (bought a grey import Motorola A780 in the US because I HAD to have Linux on a smartphone), I will honestly tell you to only buy it if you just want to wear a label. "I have an open source phone, I am therefore alpha geek!!" And I am sure it would be fun to code for too.
But if you want a smartphone to actually use, get an iPhone 3G, HTC Windows Mobile phone, a Nokia N96, or even the new Palms. Something with software support that works, secondary applications you can actually buy and use, and the ability to actually have accessories that fit it, like cases, chargers, and car cradles.
Otherwise I suspect that you will just repeat my experience with the A780...which I couldn't WAIT to get rid of after a while, despite loving the physical hardware...