Is it like a candle flickering (backlight - like you were twiddling the brightness)? Or, are there black "bars" or full screen flashes (black) re-drawing the screen?
The latter is what I've experienced. I've had the machine since the end of February. The firmware update (should show up in Software Update, if you need it) helped quite a bit. The problem almost always shows up on wake, but not every time (maybe 20% of the time, which works out to once every few days for me, since I usually leave the machine running (open)). I can "fix" it by switching to the 9400, then back to the 9600. I'm still virtually 100% sure it's a software problem. I've never seen it in XP (Bootcamp), and I never see it just using the machine (well, maybe once or twice). I could have exchanged the machine, but aside from this, the machine is perfect (no dead pixels or any of the other physical variances people have reported).
edit: forgot to post the machine info: it's a 2.66GHz. had the 5400 RPM drive, but since swapped for the WD 7200.