Safari on my Mountain Lion 2010 Mac mini at the time of install was completely useless for me. Every time I click on more than 3 websites, the entire program hangs up, beach ball comes out and the app starts eating RAM like crazy. Like gigs of ram, and I have to force quit. The processor also maxes out. I upgraded this morning from Lion using Splashtop remote desktop on my iPhone, then went home for lunch to try it out. Not sure what to do next. I repaired permissions and verified the disk for fun, no help. Example: I opened safari, clicked on macrumors favorite, clicked on Forum, program is toast, using almost 4gb of RAM before I force quitted. (I'm back at work now typing this).
(I'm hoping that this is just an issue with Mountain Lion Spotlight indexing my data, we'll see this evening when I get home).