Just installed this 42 minutes ago.
The browser itself seems fine - in it's 'stock' condition. Pages render just fine. The font-smoothing (I set it to low) looks fine on my CRT. I don't see the 42% faster bit though. I am on a measly 256kbps connection so I imagine I would be more sensitive to any speed gains. I miss Mouse Gestures the most followed by AdBlock, custom Greasemonkey scripts, NoScript etc.
I just tried visiting an infamous wares/serials/crack website that is known to try to automatically install all kinds of spyware/viruses on your computer. It didn't allow them to install (but no warnings - I was just watching Task Manager) but for some reason, the browser has been stuck at 99% CPU usage ever since.
I looked around for some plugins on PimpMySafari.com (first Google result) and all of them seem to be OS X-only.
And yes, iTunes has started crashing since installing this.
As seen here on my PC
Then again, I haven't updated iTunes 7.1 to 7.2 so maybe that might fix it. (I don't use the program but I keep it installed because my sis uses it)
One last thing: I just checked out some embedded Youtube-video heavy pages (think most celebrity blogs, Myspace profiles etc.) and scrolling through the page was smooth and slick. Some users say it's pretty jerky but I'm not seeing it.