IE8 Beta 2 is available from http://www.microsoft.com/ie.
I installed it today - haven't given it much of a workout yet but here are some first thoughts.
Standards mode by default is interesting, I think I'm going to see some odd result over the next few weeks.
I love that items in the Address Bar history can now be individually removed, the drawback with this is where they've put the button. It'sright on the right-hand edge of the dropdown area, which means if you drop it down from the arrow, it's then far too easy to click on a url and delete it instead of going to it. More usability research required here Microsoft!
Looks like security has been bumped up a bit again, which as a general concept I approve of. However it looks like it's broken our scriptlet-based menu and I haven't found how to turn the security down enough to resurrect it yet :-(