I've had nothing but problems since moving to the latest beta. I had issues with the older beta versions but nothing as bad as this. My browser hangs all the time and a bunch of websites (most notibly gmail) act really, really weird--to the point where they aren't usable. I still think IE7 is going to end up being really nice but it would be nice if the newer releases worked *better* than the older ones. It reminds me of Windows 95-the betas were a ton more stable than the final released version.
I suppose that is why I am still using the memory hog known as Firefox at home. It may suck up resources like crazy but at least it works (and I don't think I could go back to living without tabbed browsing so there is no way I am am ever going back to IE6).