I've bought a N900 few days ago, tried to configuring for my use, I've seen it's difficult for me to use it as my main phone, I'm fascinated but I can say it's very slow compared with modern smartphones, I'm not able to log in into FB and Twitter apps, don't know why, G+ don't exist and browser is too slow.
To be honest I've bought it because of neo900 project, which is very interesting and can give a new life to my n900, but actually I don't think to use it as my main phone.
BTW I have a N9 too, faster enough but I hope there will be a neo9 project in future.