Im also lookign to replace my N900 (which i like), previously had an OpenMoko Neo (which was a great talking piece, bad phone).
Im currently keeping an eye on the fairphone, they are just finishing there first batch of 25,000 phones and looking at a new order soon. Second release is usually a good one to get in one as they have had a chance to find and fix hardware bugs.
The replicant project has done a review of the fairphone, there biggest criticim of it is that it doest have good hardware isolation to prevent NSA type spying. It isnt supported by replicant yet, but say it should be possible.
It looks like the project is more driven ideology rather than profit, but that ideology is very much focused on the phone. I hope they do well.