I don't know much about QT and GTK+, but I've heard that QT is for KDE and GTK+ is for Gnome. Now I'm using Gnome and I want to use a C++ IDE. It's said that QT creator is a nice choice for c++ development so I decide to have a try. But I'm really worried about the incompatibility between QT and Gnome. Besides, I'm wondering whether it's normal to use qt creator in Gnome developing apps using GTK+ or not. And, QT and GTK+, which one is better for a ubuntu user?
One of the goals of modern releases of Ubuntu, is to bring different environments closer together. For instance, Unity 2D uses Qt, but you won't consider it a non-Ubuntu application. You should choose GTK or Qt by the merits and features of the toolkits. In older versions of Ubuntu, Qt-applications will feel somewhat out of place, but in modern versions, they should blend in nicely.
Indicators, the global menubar, etc, are specifically designed to be used by all kinds of different applications. They will work well with Qt apps, in Unity, KDE, LXDE, XFCE, etc. Except for the scrollbars, Firefox will look right at home in Ubuntu, for instance.