I have to say I'm a little dissapointed that they decided to remove the real Windows 8 start screen. But that's just one thing and I will get used to it. I'm glad what they did with apps. I like apps, it's so much better, but the full window screen can make it kinda difficult sometimes, so this is very good. I'm also excited about the new browser. Cortana we will see yet.
But what I think they still should improve is Windows Defender. I'm not saying it's bad, I'm using it myself. But few changes to make it even better. Like add a contact scan (right click scan). Another thing is perhaps addind some zero day component. For now it's only signature based. For some users like me it's okay, bit for many not. So that'd be nice