Here's what I've noticed:
Webpages load faster. Though the actual software can be, at times, slower.
It's actually equal (if not better) aesthetically than Google Chrome. It works better with the Windows theme I'm using.
Newgrounds doesn't load properly. There are gray bars on the sides of the page.
IT seems more computer intensive than Chrome.
It also seems to have taken many of it's designs from Google Chrome. Both functionally and aesthetically.
I also timed both Safari 4, and Chrome at how fast they load various websites:
Torrentz.com -
Safari: 3.61 seconds
Chrome: 8.47
Facebook.com -
Safari: 2.95
Chrome: 4.92
UPS.com -
Safari: 3.67
Chrome: 11.03
So, yes, Safari 4 is over twice as fast as Google Chrome.
I also noticed that pages you have recently loaded come up almost instantly with Safari 4. I'm definitely going to use this.