Lion is running pretty good so far. I installed it over my Snow Leopard macbook pro (2009 model), and it only took under an hour to install (not including download time which was about 30-45 minutes). It was quite buggy in the very beginning. A couple of app icons on my desktop would not show up, and when I would quit Chrome, it would close the window then freeze, I wasn't able to see the status bar at the bottom of windows, and I didn't like the reverse scrolling, or new mail look. However, with a few tweaks to the system preferences, and playing around with it for a little bit, I'm loving it.