In my experimentation here so far, one huge change is the amount of linking they do to your Windows Live account. They want you to log in using it, and presume a connection. I'm sure it would work without one, but only halfway. They'll have a Windows Store similar to Android or iOS, which they *tried* to do with Windows Vista, but it never took off. On the ARM platform they will be mandating it, since they can 'start fresh' there. I just don't know. It's clearly a tablet oriented OS. Using it with a mouse is ... I just dunno. Maybe some will like it, I'd like to get the opinion of an average Joe instead of myself. With Metro, everything is nice and big (to be touchable and readable on tablets). It does
seem snappy, I'll give them that.
Once you get past Metro, you are in a VERY modified Windows 7 desktop, one without a Start Menu, which is soooo awkward. It's also NOT Windows 7, because it's been changed a lot in other ways. Why they wouldn't keep an OPTION to restore the Start Menu, I dunno - like you've mentioned before. It makes little sense. I guess they couldn't make it touch-able, so they decided to remove it, but dunno why it's not restorable. Without it, you kind of fumble around (or I do).
You can hit Start+F to show a search box that can search for applications, files, etc... but applications, for instance, are not sorted like the Start Menu, they all shown on ONE LEVEL (e.g. no sub-menus) and all in big blocks. It's just awkward.
Pressing the Windows key brings up Metro .. which is just like Windows Phone's failed interface.
There is an increased level of per-application permissions, which is good. For instance, it tells you 'You have a new app that can open web pages' as I install something. It doesn't block or stop it, but tells you that, briefly, in the upper right corner (a new area for notifications).
The mouse interface is improved in the CTP. You can click and slide a little and the screens will 'just go', instead of having to drag them. Specifically speaking of the login screen, which shows a clock you have to first click past before you can log in.
The mouse scroll bar can be used the slide the Metro UI screen left or right, or Metro apps.
EVERY start menu shortcut you have gets displayed in the Metro UI, making it quite awkward because it shows all sorts of stuff normally buried in the Start Menu - at least in the case of third party applications. Each gets their own square.
I just dunno .... that's about all I can say. This will be great to get Microsoft into the tablet game, but are tablets really the future, or just an ancillary mobile device? I think the latter.
PREDICTION: The majority of traditional PC users stay with Windows 7.
The good news is Process Lasso sure works great on it

. There is some tweaking I'm doing already for it, but it already behaves just fine.