Tried it. Still has holes; went to a page that tried to load a malware but was caught by Avast, not IE beta 9. Went to a page to try HTML5 demo video. Didn't work. Went to youtube, tried to choose a video from the search drop down list, didn't do it either.
Now, compared to the useless IE8, it is way too fast!
Since this is the first beta, it is understandable that many things won't work, but now it looks like Microsoft is getting serious about developing a good browser; it seems like Chrome and Opera are giving them heat. I wish I could say the same for FireFox, but their latest drop is disappointing, it's slow and sometimes it stalls loading pages, something that doesn't happen with Opera.