While 7 was/is good, there are still plenty of improvements that can be made, and this is something that Windows 8 DOES bring, but shot itself in the foot be forcing a new UI on top of it, whether it was needed or wanted (and only half implemented).
In many regards, I do feel kind of sorry for MS with this backlash - too much time has been spent complaining about the UI, when in fact it's only a part of the package. The underlining architectural changes and usability tweaks have pretty much gone unheeded. There are other things though that still worry me.
Live ID accounts are in effect cloud logins for windows machines, and are currently optional, as you can still create local accounts. But it's what happens after, that concerns me. Will later versions require Live ID? A resounding 'hell no' would come from enterprise, but it wouldn't surprise me if MS tried to sneak it in via Active Directory or one of its complementary services tied to Server. Even if you decide to take advantage of the Live ID account, MS security has a bit of a shady history. It can sport all the 256-bit encryption it wants, but security breaches are rarely the result of cracking the data stream, but man-in-the-middle, social engineering, guessing passwords or some unforeseen loophole - the latter being the most prevalent.
On the good side of things there is the revamped multi-monitor support. File manager is now back to the same level of usefulness as Windows XP, but with a few more improvements (open command-line here). Task manager and resource manager are a lot more useful in tracking down misbehaving apps; now with the ability to dig into what specific applications are hiding behind 'svchost.exe'. A whole mass of library optimising and general system improvements, resulting in a more efficient and faster OS (according to a number of benchmarks using the RC edition, but we'll see with the final when it comes out).
There's the inclusion of anti-virus by default. Hyper-V pre-installed for virtualizing. But it screws up again (kind of), by removing DVD decoding by default. This isn't a huge issue anymore, there are so many players out there, plus converted formats like h.264, and streaming services like Netflix.
Still, it can't be avoided. In order to access and use all these new features, you have to use and get past... the Interface formally known as Metro.