Now on Beta 8 and running fine.
I am not so happy with right-clicking the back / forward buttons to access page history, or the use of the main URL bar as the preview location for URLs as well, but that's just because of habit - and is nit picking.
I use IE8 at work, and I have IE6 and IE7 at home for testing.
FF4 is streets ahead - I don't use half the features, though!
SD