Looks like the flickering has returned for me. After several weeks of having no problems, the flickering has returned. It's still not quite as bad as it used to be, and some days it only ever flickers a handful of times over the course of a couple of hours, but it has definitely increased again.
I've heard people having graphics issues with 10.7.2. Perhaps that's the problem. I also have a problem with graphics glitches after the computer wakes from sleep with my external monitor, in this case a Samsung TV.
After I enter my password on the lock screen, the desktop becomes a gray colour and the menu bar is messed up. Parts of it show, and parts of it are black. Mission Control looks very weird as well. The only way to fix this is to log out and back in.
In order to avoid it I've woken the computer before turning the TV on. This seems to prevent this problem.
Anyway, perhaps a simple reboot will fix this flickering. But even when it was "fixed" before 10.7.2, it still flickered once every couple of hours. So the problem has never completely vanished.