I finally upgraded my MBP to Lion last Friday and, on the whole, I really like it but there are a few changes that just boggle my mind. For instance: why the hell does closing the lid now put it into single-monitor mode instead of putting it to sleep like it used to? I could understand if, like the change to how scrolling on the trackpad works, it was changeable back to the old way, but from everything I've seen, it's not.
It's just annoying that they've changed something so fundamental without an option to change it back. It's annoying to close the lid without thinking only to have everything push over to my second monitor, then have to reopen the lid, re-detect the monitors and, finally, put it to sleep with ctrl + shift + eject.
Other than that, I love the iCloud integration, the iOS features and all the other little things changed to make it better (like being able to resize a window from ANYWHERE on the border, not just the lower-right corner).