It's more aimed at web developers, but from what I've seen, the performance is very promising, and the CSS 3 and HTML 5 implementations are improving with every public build. The rendering of pages, are sound.
However, given the current SunSpider results in JS execution speed, it looks unlikely that they will further enhance the JS engine. As such, any more improvements would be on a very miniscule basis, of the order of 1000's of a millisecond.
If you're interested, try it here. I do wonder what is your opinion of it, if you have used it. I don't really think comments such as: "IE is rubbish whatever they do", or to that effect are particularly constructive and useful.