There is a highly experimental Krita installer for Windows
here, but the 2.7 version seems to not work with tablets which sort of defeats the point. Seriously, if you want to experience FOSS software in the fullest, you should really use Linux. Set up a dual-boot and run Windows and Linux on the same machine - that's what I do (I only use Windows for gaming anyway).
MyPaint is certainly a lot easier to set up and use - one of the drawbacks with Krita is that you need a truckload of dependencies, including the massive Calligra KDE library. To be fair GIMP-dev requires a lot of latest-level libraries compiled too. The boon with using powerful external libraries is of course that they get a lot of functionality for free (the damn program even supports Inkscape-like vector graphics mixed with normal bitmap graphics as well as CMYK and 32-bit colour and plenty of other really nifty stuff). It's still very much pre-alpha though and whereas Krita offers a lot of features that GIMP yet doesn't, it's also a lot less stable nor as ubiquotous as GIMP of course.
@Moko: Aye, the image is not all that exciting, but as the caption says, that was also not really the point.
@merrak: A drawback of using non-rolling releases.

I'm just in the beginning of testing out Linux Mint myself, after having used rolling-release Debian SID for many years. Will see if I can stand a fixed version system or not. That said, you can still run any version of programs, including GIMP2.8, you just need to install it yourself from some other repo than Ubuntu's official. Ubuntu is still Debian under the hood after all.
@kimppi: I'm not fully convinced about how the vector tools are presented to the user in Krita; It adds a lot of confusion to the beginner for sure. The tools for vector work is confusingly similar to those for bitmap - trying the vector tools I've found the program (without telling me) creates a vector layer - on which bitmap tools will not work. In previous versions anyway (didn't try it with 2.7), you would then remain on that vector layer also when switching back to bitmap tools - I know to separate vector from bitmap now, after having read up on things. But it does feel like the program hangs/bugs out to a casual first-time trier. Once getting that, having vector graphics in a bitmap program is pretty innovative.
I really like MyPaint for its simplicity and clean UI - I like to just have a canvas and keyboard shortcuts for everything. Krita is more involved in that regard.
.
Griatch