Active N900 phone user for a year now and planning to move to one of the following 3:
N900 - exciting low level stuff is worked on that seems to give us an option to have an up-to-date kernel with a more recent software stack.
I have a couple of spare N900's in mint condition so I am ready for the future
Neo900 - depending on final price, product and availability.
Any new phone with keyboard that can run some kind of 'Linux flavour'