Earlier quoted context omitted.
Seems like all the reports are on the _2011_ version, with isolated incidents on the 2010 version. 2009 is mentioned nowhere.
My Fall 2009 model overheats and locks up and crashes when playing games like Starcraft 2 or Left 4 Dead 2. That's not to say every notebook from 2009 had cooling problems, but some certainly do.
I don't expect to see any kind of lockups or grey-screen, ever. It just shouldn't be part of owning any computer, especially a mac.