Why should user use Qt?

Advantages of Qt over other languages.

1. One of the biggest advantage that Qt has is cross platform. User need not to change a single line of code to build on different platforms.(I did not get a chance to develop something on Linux + Qt)
2. Working in C++ gives you great control, the possibility to work with fantastic libraries like STL, Boost, etc; and your code is compiled to native binaries that will run at full speed without the need for a virtual machine.
3. It uses system's resources to draw windows, controls so even though you will have the same code for different platforms but your application will get the native look. Which is amazing feature from user point of view.
4. Very rich and well developed libraries. Lot of supporting tools like Qt creator, designer, etc.
5. Last but not the least it is open source. :)

So enjoy new application development with Qt.