OS X 10.7 (Lion) has been out for about a week and although that's probably not enough time for any subtle bugs to surface, it is, apparently, enough time for my natural paranoia to be overcome by my desire to give it a spin. So over the last couple of days I've updated my machines with Lion—the upgrades went extraordinarily smoothly; thanks for asking.
I'm still getting used to the OS so I don't have much of substance to say right now but I can comment on one issue that's getting mentioned a lot in the reviews that I've read: scrolling. If you've been paying any attention to Lion, you know by now that Apple has “reversed” the scrolling. Swiping down with two fingers used to scroll towards the bottom of the page; now it scrolls towards the top of the page. It's easy to reinstate the old behavior with the System Preferences pane but that hasn't stopped the howls of anguish—not to say outrage—from many of the commenters.
The idea is that the new behavior mimics what happens with iOS when you scroll: you're grabbing the screen and pushing it up or down. Despite having a small problem with muscle memory, I like the change. The old behavior never made sense to me and only muscle memory and the fact that it had always been that way kept me from being totally confused. If I thought too hard about it I would do the “wrong” thing. After only a few hours the new scrolling already feels natural. Sometimes I start to move in the wrong direction but that is already starting to die out. If you're having trouble with the change, just imagine that you are putting your fingers on the text and pushing it in the direction you want to go.
I'm sure there'll be lots of kvetching and dark mumbling about Apple oppressing their users and upsetting the natural order of things but, really, all Apple has done is finally have scrolling make sense. And, you know, if you really, really don't like it, it's easy to change it back.