Comment 21 for bug 481373

I also have exactly the same issue. Although it doesn't just happen in compiz, it also happens with metacity when compositing is enabled. If compositing is completely disabled then it is very fast, but I get a message saying Docky needs compositing enabled.

It's definitely the tooltips causing the problems. Even with the zoom disabled, I can see the tooltips are very laggy when moving the mouse over the dock (both in compiz and metacity with compositing enabled). I also tried in compiz with all of the window animiations disabled and it makes no difference.