Yes, the Genius Bar does have a test. See below.
My experience on the 14th makes it clear that not all 8600M's are affected. (At least that's what Apple thinks)
After my latest graphics issue I took a picture with my cell and decided to do something about it. I brought my MBP 2.2 SR 8600M 128 into the local Apple Store (SLC, UT) to have my SuperDrive replaced and my graphics card looked at.
The Genius Bar has a new 8600M diognostic test that runs off of an external HD. The software specifically looks for the 8600 defect. After freezing on the first test and showing crazy color patterns, they tried it again and it passed. If it had failed then they would have replaced the logic board.
They told me that my graphics issue must be software related and has been a known issue with Nvidia's drivers. He wouldn't say how long it's been a known issue, only that they are still waiting for a fix.
I've had my MBP for a year and 2 months and experienced this for the first time only 2 months after purchased. Yes my unit was a refurb and has Apple Care.
I personally don't believe this is just a software issue. It's happened under 10.4.11 10.5.1 10.5.2 10.5.4 10.5.5. All random and not reproducible. In all i've had this happen 12-15 times.
This is the picture I took. The Geniuses sent a copy to Apple HQ along with a profile of my machine.
http://www.curt-sanders.com/MBP_SR_2.2_8600_Baslistic_Graphics.jpg
I've posed in apple's forums looking for suggestions and emailed Apple Support last night asking them what they think I should do.
Any suggestions?