Which graphical environment (MFC, ATL, QT etc.) should I concentrate on, in order to be more employable? I don't want to spend months learning something only to discover that "no one" really use this or this really sucks, and "all" pros are using only such and such.
Take a look at WPF. It is the successor to Mircrosoft's MFC. Mastering it could provided you a qualification "older" programmers might not have yet.
Regardless of the technology, I would make sure that you understand and can demonstrate sound programming practises surrounding implementing solutions in these technologies (e.g. separation of concerns, understanding the MVC pattern).
Toolkits come and go, but those practises are key. I would happily hire someone with an understanding of these despite their lack of knowledge in my particular chosen toolkit.
Qt is I think the most interesting.
- The API is very nice
- the documentation is excellent
- Friendly licence (LGPL)
- The IDE (QtCreator, but you don't have to use it at all) is simple but efficient
- It very multiplateform (Win, Linux, MacOSX) and gives a native feeling on those platforms, and recently
- Big Companies use it (Google Earth, Opera, Skype...)
- Since it has been bought by Nokia, the development is rocket fast
I would also add wxWidgets and eclipse Rich client platform.
when I last looked at it, wx was somewhat simpler than QT.
On the other hand, eclipse RCP provides a lot of functionality right out of the box, however it is overkill for small projects.
Compare the number of jobs on various employment web sites for each technology you are asking. I believe MFC is still in most demand, but may be wrong.