>>1
What do you have against WinAPI? You do realize that if you use windows, almost all the programs you use are written in WinAPI besides newer applications like office 2010 and newer. For example here are some things written using WinAPI:
-Windows Live Messenger
-Foobar music player
-Winamp
-All versions of office and visual studio before 2010.
-Chrome browser
-Firefox browser
-All games
-Windows media player
-Adobe Photoshop
-Fruity Loops Studio
-And pretty much everything else
Most people avoid WinAPI because its too hard to program in. GTK/QT/WxWidgets are in comparison like toys since they are so much cleaner in terms of an API but lack the power of WinAPI. But look at those examples above and you will see that it is indeed extremely powerful when used well. When was the last time you saw a UI written in GTK/QT/WxWidgets that look as good as those programs mentioned above? In the end, professional applications written for windows are written in WinAPI/WPF because professional application vendors can pay lots of money for smart programmers that can take the heat of working with complex APIs.