Mine's not activating either...it gives me an error about thier activation service being down or something like that.
But I love what I've seen so far. I really like the way they've redone the menu system with the tabs at the top. And I'd have to say my favorite feature is (in Word anyways) if you highlight some text and move the cursor to the right of what you've highlighted, the little menu pops up and you can change text style stuff right there. There are so many little things I love.
And in excel, they've gotten rid of the terrible graph colours!!! Now you have options to make really nice looking graphs!!
And apparently this beta expires in February 2007...