Trust me, it's worse in real life than it is in the video I took. Compressing the video footage actually smooths it out just a tad. When you see it on my computer screen it's ghastly.
It's not so much of a stop, go, stop, go as it is a go, jump, go, jump. It's like the rendering skips ahead a few frames and bits of the surroundings teleport a few inches ahead of themselves.
I really bloody hope it's a power supply problem, I've had a couple of games crash on me recently, and from what I hear that's one of the symptoms. With my luck though, getting a new PSU won't do a damn thing.