My main annoyances are the monkeying around with both the traditional process lifecycle for GUI apps, and the saving/loading of documents. I gather there has been some refinement of these (or at least more options) in 10.8, which I'll try a couple of point-releases in.
There's that, and also monkeying about with the trackpad (reverse scroll is okay, three-finger drag is very awkward for me), as well as hiding the Library folder, forcing use of the App Store to get Xcode, Xcode constantly crashing... I feel like I'm not part of the target market anymore.
