I am currently looking at starting a project in Unity 2 in the coming months, but I’d like to be able to take advantage of the porting to XBLA feature of Unity 3 when it comes out. Would it be possible to port one’s project from Unity 2 to 3 without too much hassle or would it be better to start from 3 at the outset?
As far as I know, there shouldn`t be any problems updating your unity project from 2.6.1 to 3.0. You may have to do some small tweaking here there, but other than that, you should be fine. Just make sure to have a backup of your 2.6.1 project, in case something should go wrong during the update progress 