My friend from school gave me a copy of the mountain lion recently and i have been debating whether I should use it or not. He told me he got it from his dad (who is a developer), but, knowing him, it is probably off of some pirate torrent. I am fairly new to apple computers, but I consider myself a pretty tech-savvy person. I really want to test out the new features and everything. I just have a few questions. I made a complete time machine back-up. 1) Is that all i need to do for that if i need to restore if something goes wrong? I also have the lion usb recovery (becasue I have a 2010 air and it came with one). 2) Would i need to wipe my computer before installing? I have the 128gb version, so a separate ML partition is not possible. 3) For people who have done it, are most of the apps you use compatible with ML? 4) Are there any problems I might come across when doing this. I know some will say i should just wait, but I do not want to wait if i don't have to. If this is relatively risk-free, then I want to do it. If I am unable to install over lion without losing things, could i restore my files with a lion (time machine) back-up while maintaining ML as my OS? Thanks in advance!