So Safari 4 Beta is out 24 Feb, 2009
Looks great, has some super features, and the HTML 5 support is excellent. I had issues using the browser with Google Apps Mail, so for now I will let it lie, but otherwise I am impressed.
Update: if your Google mail isn’t working, try this: grab the URL for the “basic” HTML view for mail, and open that in Safari. Should work fine. Then switch back to the standard view. Quite why this fixes things when clearing cookies / cache / history / offline email doesn’t, I have no idea!