Flash causes my browser to become non-responsive every day at least once. But then I'm using 64-bit Linux with Flash Player 10 which is still in beta IIRC. Even so, it's the most noticeably poor aspect of my web experience. I could go back to FP9 but it was not much better and I don't want to loose full screen video.<p>Oh, that's one more plus for switching to Chrome browser I hadn't realised (I've been using Chrome for a few days exclusively; I do web dev so this is a big thing).