This isnt a perceived problem I have it too and it is very very annoying.
Safari will literally freeze to the point of becoming completely unresponsive and showing the beachball of death on pages with large animated gifs that display with no problems in firefox. This is a big problem on a lot of forums. I've also found several other people reporting the same problem while googling for a solution.
To see it in action go here:
http://www.neogaf.com/forum/showthread.php?t=355091
once you scroll down to the section with the animated gifs it will soon become completely unresponsive (beware that this will freeze your safari for a while and it might be a while before it becomes responsive again and lets you close the offending window).
overall performance with animated gifs also seems to be much worse than other browsers, even when it doesnt freeze completely.
i tried a webkit nightly recently and this still wasnt fixed