I just finished updating and I'm kicking myself for it. Number 1 reason is that Microsoft is now forcing you to sign in with a Microsoft Live account and won't proceed without one. It has also screwed up Firefox.... NOT HAPPY.
ETA: Just finding one thing after another that it's fucked up... My D drive has been churning like mad ever since the update completed and won't stop even though I told Windows at the setup not to sync anything at all. The D drive is a mechanical drive with nothing but data - nothing the OS would need to look at. Windows is installed on C:, which is a 120 GB SSD.
ETA2: Now this fucking thing popped up in the upper left-hand-corner and will not fucking go away and I can't click on anything behind it. FUCK YOU MICROSOFT!