Lion can easily and definitely be downgraded to the far more stable and proven snow leopard. If you call apple tech support they will be emphatic -- it cant be done, we dont go backwards, it will cause damage to your machine. For whatever reason that is a LIE. i then went to my apple store, no questions asked the genius took it in the back and 20 minutes later voila snow leopard running on it so i now can use my ms office 2004 with no problem. It would not run under lion and thats the only reason i downgraded. Why apple is saying it cant and should not be done is a mystery to me. My genius said he dud it to his machine too bevause if incompatible software with liom that he had. I even brought my leopard and snow leopard disks with me and he said he'd use their own. When he brought it back 20 minutes later it had 10.6.8 and when i got home i loaded office o4. Dont forget snow leopard wss on the early 2011 mbp BEFORE lion was introduced.