Lion was one of those OSes I consider a between OS, due to the fact that it included some new feature that looked half baked when Mountain Lion came out, and included bug fixes from SL. ML is a fully fledged OS, great iCloud features, new Safari features, gestures, a bunch of stuff. Definitely a great OS. Sad part is the original Mac Pro can't run it, which is a bummer because I wanted one for video editing. It requires a supported video card and EFI64 emulation.