At least twice after leaving my mbp open and the display having fallen asleep, when I have tried to wake it by clicking the track pad it did not wake. I've had to turn off the computer and turn it back on by holding down the power button. I'd like to know if this indicates a problem with the software or hardware (maybe the hard drive?). I'm hoping OS X Lion would resolve this and other issues I have experienced in the past with SL - such as a pixelated window sometimes in Safari when moving back and forward between sites after having many tabs open, sometimes in iTunes, e.g changing from iTunes Store to Music Library I'd see some scrambled image for a second and then it's normal, and I having to hold down the power button to shut down after the computer would not shut down as I'd selected.