I along with quite a few others it seems have had a problem with Safari 5 being incredibly slow and sometimes not loading sites at all. The loading bar would get to roughly the end of http:// and then hang and usually bring up a message saying the server could not be found. I knew it was a problem with Safari 5 because I had installed it on all my home Macs and the ones at work too and ALL of them had the same problem. I have now found a way to stop this happening and its to do with DNS servers. Simply go into System Preferences > Network > Select you internet service (be it Airport, Ethernet etc) then click advanced and under DNS put the following numbers: 220.127.116.11 18.104.22.168 (These are apparently Googles DNS servers). Quit Safari and relaunch and now you should have a super 'snappy' Safari 5. I don't quite understand why this works or what DNS servers actually do but it seems to do the trick. So this is a very easy work around until Apple fix the problem.