Awful. Just awful. To me, that is one of the dullest logo changeovers in history.
The MS UK site still has the old logo - comparison:
I think the previous MS logo is iconic, distinctive and timeless (i.e. it will never look dated), two things that only the best few logos have. I know that they are trying to match the whole 'simplification' thing that's going on, but changing the logo is going too far. Looks a bit like a fad. In five or six years I guarantee that it will look old fashioned and out of date, and they will be forced the change it again.
The previous one has lasted since 1987, stood the test of time and still looks fresh and modern. It's also a lot more interesting, and this new one just... isn't.
£5 says they change back in five years.