I can't say I'm particularly excited. I've been using Linux on and off for the last 10 years, and almost exclusively for the past 3, and find it a much more pleasant OS to use. And it seems all of the new features everyone has been praising about the most recent versions of Windows -- the increased security of Vista and 7, the redesigned taskbar with pinnable apps -- all seem to be things that other OSes such as OS X and Linux already had. Unix-based OSes have always had better security, and the User Account Control's method of temporarily granting administrator privileges seems awfully similar to the use of sudo in Linux. The Windows 7 taskbar is a fairly obvious copy of the OS X dock and similar docks available for Linux. And the list goes on. Hey, I was one of the first people I know to try out Windows 7 when it was released (and actually a bit before, since I got my hands on the beta), and I told all of my friends then that it was the best version of Windows yet. But it really didn't bring anything new to the table.
As for Windows 8, from everything I've seen and read, it seems more like an upgrade to Windows 7 rather than a new version, and the new features don't really look that appealing to me. The rumored inclusion of an app store is nice, but Linux distributions have been doing that for a long time and for free in the form of software repositories. And since the iTunes App Store and Android Market have made the idea popular, Windows just seems like it's a bit late to the party. The reported ability to boot faster is nice, but Windows has always been rather slow to boot compared to other OSes in my experience, so it seems a bit more like a correction of a problem rather than an improvement. The new Start Screen looks like an up-sized version of the Windows Phone 7 interface, which I personally don't care for. Also, the tiles do what could just as easily be done by desktop widgets, and putting them on a special screen just means it requires an additional click to get to the desktop AND that those things aren't visible while I'm on the desktop. Widgets seem a better idea in both respects. On a related note, I don't think the increased focus on touch screens is necessarily a good idea for what is primarily a desktop/laptop operating system. There are very good reasons why tablets and smartphones have touchscreens while desktops and laptops generally don't -- a touchscreen is a great interface for a portable device, but on a computer for which the primary uses require a greater amount of data input, it's a lot easier to use the mouse or trackpad located next to the keyboard rather than to take your hands away from the keyboard to swipe around the screen.
I'm sure Windows 8 will be a great OS, especially since it's building on Windows 7. But I haven't seen anything that's really new about it, except that those things are new to Windows. Many of the new features are things that other OSes have had for a while now. And I just don't think there's much there to be excited about -- unless you've never had any exposure to those other operating systems and don't know better than to think that Microsoft is actually being innovative.