I popped it on my machine last night. So far, so good. I've been running beta 2 bits successfully since late March with hardly any issues. Looks like they snuck a couple of minor new features into this build, including the ability to finally customize the new icon bar to the right of the tabs.
One other UI tweak I noticed that was not metioned on the IE blog (at least not yet) is that they have reduced the real estate taken up by any toolbars you have installed. For example, the Windows Live toolbar and Links bar I usually have turned on use less vertical pixels than before. That's nice.
You can grab the beta here: