Jittery dock and drag windows animation

Hello.
I was really confused, when I first started dragging a window in ML - and the window started jitter.

Dock is also jittering like a mad rabbit, when I slide over it.

Scrolling of long pages in safari (and anywhere else) - same nasty jitter.

Switching between desktops? No, you don ask me!!! It's awful.

It looks weird. Weird for the "most advanced" OS in the world.

Yes, I know I've got old mac pro (early 2008), and not-so-new video card (ATI Radeon HD 5770) But jittering windows is way to much.

After all my mac is still in the list ))

Lion did well, Snow Leo and Leo they all could do it smoothly.

Any ideas?