I just came here to see if anyone else was having problems - found your post.
For me, the issue seems to be memory usage. After a long session of web surfing, memory usage goes way up (virtual size over a gig). 'Resetting' safari to clear cache/cookies/history does not free up memory.
Clearly, with that level of memory usage performance slows to a crawl (I have 1Gig in my G4 powerbook). Is there now a memory leak in Safari?
This definitely started after the latest update.