I installed Lion on my 2009 MBP on the 1st day it was available. Since then every day Lion locks up at least once a day. The mouse would move and I could activate some menus but nothing worked. The only way I could exit was to hold the power button down until it shuts off. This happened with various apps and the only thing that was common to all lockups was that the Time Machine icon was rotating and I assume it was active. I tried waiting until the TM completed but it didn't stop after a very long time so I don't think it was actually working. I have now shut off the TM and disconnected it and I have had no lockups since. I'm sure Apple has a bug in Lion effecting the TM and I hope they solve it soon. Otherwise I like Lion but some features take time to get used to.