1. I'm not sure about Ubuntu and i don't think it'll work, it'll be laggy as ****.
Personally, I would go with a different device. N900 has a piss poor battery life, and i've tried out tons of mods and tweaks to increase its battery life, even sacrificing performance, but it's still crap. It's a good phone, but battery life is one of the majority issues that users have had with it.
Personally, i bought the device just coz it looks sexy
Windows Phone 7 or Android is at least more promising, and I doubt Meego will do well, one can only hope for it to. That's just my opinion anyway
PS - Feel free to send your E90 to me. I've always wanted that phone