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Partly, I have read this article. I though that maybe someone had experience working with it and could share it.
Qt is for cross-platform GUI development -- it isn't a sketch tool like Processing, and it isn't focused on providing accessible entry-level programming.
If you are interested in something Processing-like in C++, instead of using a general purpose GUI toolkit like Qt, perhaps check out OpenFrameworks.
If C++ is already familiar or you are looking to learn a new programming language, this might be an advantage -- for beginners the key thing to understand is that programming C++ is quite different from Processing (Java) and has unique challenges.
For Qt user feedback, I would recommend the newbie areas of Qt forums -- e.g.