It needs to start with the veterans first and end up with the normal users last. With veterans saying my N900 is better or my N9 is better, this is brought about to other users thinking or following their lead. Both have their qualities and both should be more than willing to set aside differences to make the best of each platform. I'm sure some diehard N900 users have something they can offer to N9 users and vice versa. We just need to find the common ground first.

Edit: Before anything can happen, the hostility towards Harmattan needs to end.