I;m running it on my Mac Pro and it does seem a little faster. It does crash occasionally when I open it but other than that its fine. I like the new search window(opens at the top of the browser rather than a new window) and spell check
I tried the beta on my iMac G5, but not on my MacBook Pro. The first noticeable difference is the same of any upgrade - SAFT plugin stops working. That alone seems to speed things up, though.
SAFT is a trade-off between features and performance. At first, I didn't think the Safari beta would work at all. It seemed to hang there with an error message about SAFT for 10 minutes. Right when I was going to Force Quit the thing, it decided to play nice and has worked well since then.
However, I'm not sure that it's much of a big deal to me right now. The only visible difference I've noticed is the change in Search. Otherwise, it looks like the same old Safari to me.
I would like to try Safari 3.0 but not until I can get rid of the brushed aluminum background--it's too hard to read the print. I like the cleaner, clearer look I get with safaricon and iriduim. Hopefully Apple will have the final version available with downloadable themes like firefox already has.