Related to this question, I am considering building QGIS with qt5 (caveats acknowledged) in order to improve rendering speed with qt5's OpenGL support. Before I attempt this I need to know whether QGIS (2.8/2.10) built this way would actually use qt5's OpenGL capabilities for improved rendering.
Can anyone confirm this and perhaps provide a guide as to the degree of rendering performance increase one may expect over a standard qt4 build (obviously context dependant, but order of magnitude indication would be nice)