The video (requires Silverlight) depicts a couple demos from the IE9 Test Drive site, which is home to well over two dozen different browser-related tests. Of two tests shown, IE9's performance was smooth, mostly remaining above 50 frames per second in the first and 25 in the second. Meanwhile, Safari 5 was barely able to crack double digits and actually dipped to 1FPS more than once.
What does that mean for everyday browsing? Well, we'll just have to wait and see. It's worth noting that things aren't so pretty for IE9 in other benchmarks. The recently released Platform Preview build lags behind the competition in Acid3 – but again, it's not completed yet. You can download the IE9 Platform Preview here, but realize that it's a pretty raw experience right now.