in the near future I'll be transitioning from a MBP w/snow leopard to a MBA w/lion. I have time machine backups of my MBP, will there be issues using migration assistant to move my user account over? how should I transition my <user account> over without bringing all the old leopard previous OS files, preferences etc to get as clean as possible architecture? what is the minimum tiger install space in terms of GB? I ask because I'd really like to not buy the 256GB SSD and stay under half of the 128GB SSD.