I have a 13" MBP running Lion 10.7.2, and I recently went to iCloud.com and tested out the Find My Mac features. Pretty accurate, actually, as far as location goes. Unfortunately, however, the Remote Lock feature seemed pretty worthless when I tested it. Using my Mac, I ran Find My Mac and located where I was. Then I clicked Remote Lock. Nothing happened for about 5 minutes. Then I got an email saying "your computer was successfully locked," and it told me to enter the password I set online to unlock it. Well the only thing that happened was that the computer restarted. Not exactly a lock, if you ask me.