Not sure how long it's been in public beta, but I just downloaded it this afternoon.
So far so good, some pages loaded faster but there were a noticeable glitches.
It crashes less when I view forums like wiichat, or check gmail. But I can't seem to view my emails from live.com. The interface won't respond. So I have no way of viewing my hotmail emails without outlook.
Some new nice features like viewing bookmarks/history pages in coverflow are great. But 90% of the time there are no pictures, or the pictures load 20 seconds after viewing an item. Which worries me, I don't exactly want to view the sites, and my bandwidth would be sucked like no tomorrow everytime I make a search. I'd expand the cache, but safari limits it to 500MB max. The search function does include content in a webpage, which could be useful at times.
Top sites is great, nothing new however. It's just like opera dial but with snazzier graphical interface. Unfortunately I can't seem to find a way to customize the sites that appear on this page, you can only delete one and another appears automatically to replace it. No control on what sites you want whatsoever. Fairly aggravating by the limited customization.
Tabs are on the top now, just like chrome. Integrated developer tools are great, but also achievable with firefox addons. Things like bonjour support would open up some great possibilities, but a feature similar to stumble-upon or genius (itunes) would be a pleasant addition.
This is the mac leopard build, windows should be similar. You can download it from the apple site.