No I haven't and I won't. Nothing personal to ms. I am not particularly technically minded but I have friends that are. They say quite simply "Let the others be the guinea pigs". So wherever I see the word beta I avoid it. When somehow IE8 Beta or when as now IE7 is still going strong I somehow accidently downloaded IE8 and had minor problems and a major - key parts of ebay simply wouldn't fuction so I downloaded Firefox and problem went away. I then found the ms "fix" and ebay is now useable againg but not as good as on IE7.
I emphasise nothing personal just advice and personal experience.