yea, flash is hopefully going to die soon. It's absolutely horrible. People call it "crap player". I have a pretty decent computer but i also did notice a performence drop. It's just more demanding... You might be able to go back tough by uninstalling and installing 9 again.
try installing more ram, or put priority on the flash process in task manager. If the flash you are talking about is in the browser, and not the actual program of flash, then put priority on either iexplore.exe or firefox.exe. Just right click on the process>set priority>...
