Quite frankly, Lion is a complete mess. I downloaded it and installed it over a Snow Leopard system that was working flawlessly and had never given me any problems. But after installing Lion all sort annoyances started to emerge, the biggest one has to be the tendency of my MBP to just shut down randomly, for no apparent reason whatsoever. To illustrate, here is what happens: 1- Say I am using any application, Fireworks, Chrome, Espresso, etc. 2- Out of nowhere, my screen goes black and the led light in the MBP turns off. 3- But the computer remains "on" but I can't wake it up or anything. 4- I have to force shut down the computer by holding the power button and then turn it on again. My MBP had never done anything like that before installing Lion. My specs are: MBP 15" i5 2.53Hz 4GB of Ram 500GB HD At work I use it with a secondary display, using both screens. At home i use it in clamshell mode. In both instances I use it with a separate Apple keyboard and mouse. Any help is appreciated.