If I go to a site that has a Java Applet, I can't use the applet or it slows the entire machine down and eventually freezes up Safari.
I have to close out Safari by going to the App Monitor and force quitting.
Of course, I seem to have to do this anyway after a full day of using Safari - I actually just asked a question a little bit ago on here if that was known behavior or if I was doing something wrong.
It is a shame because Safari is so much better for general use than the other Mac browsers - but this problem is truly awful for those of us that use web applications where it is not a good thing to crash/freeze in the middle of it (trading stocks as an example).