I highly recommend the use of the Qt Libraries for several reasons:
- The Framework is freely available for Windows, Linux, MacOS X, and a couple of mobile systems. Since version 4.5 the license is LGPL, which basically means that you can use Qt even in commercial applications.
- The design of Qt is out-standing, e.g. they use modern design patterns and a very consistent interface design (I don't know many other libraries that use object-oriented ideas in such perfection). Using Qt is the same as using Boost: it will improve your own programming skills, because they use such beautiful concepts!
- They are bloody fast, for instance in rendering (due to the different back-end for OpenGL, DirectX, etc.). Just have a look on this video and you see what can easily be done with Qt but is hard to achieve with native Windows, Mac, or Linux programming.
- They have a really great documentation, with tons of tutorials and a very good reference. You can start learning Qt easily with the given docs! The documentation is also available online, so have a look and see by yourself.
- As mentioned before, Qt is cross-platform; you have one source-base that works on all the important operating systems. Why will you limit yourself to Windows, when you can also have Mac and Linux "for free"?
- Qt is so much more than "just" the user interface; they also offer network and database functionality, OpenGL bindings, a full-working web-browser control (based on WebKit), a multimedia playback library, and much much much more.
Honestly, I wasted a couple of years by developing software natively for Windows, while I could have been so much more productive.