Comment 6 for bug 476995

I've also experienced dropped keystrokes. I'm not sure why, but the keystroke dropping and unresponsiveness appears to be correlated with Flash either not responding or getting sluggish.

I also use the acrobat viewer plugin, which has shown a noticeable decrease in its stability, usability, etc. with newer versions. It shows little yellow boxes with no content on the screen (they go away if you click somewhere). The page scrolling is choppy, and often results in the remainder of the page not being rendered (fixed if you skip a page ahead, then back). Like above, I have no idea if any of these issues are related, but they tend to happen at the same time.