I did some experiments with the OpenGL Renderer from Blender. The first thing i noticed was that in many cases it would be enough to produce great animations and it is really fast. You will have to leave out refractions and real mirrors. But how often do you need this features?
The worst part of the OpenGL Renderer are two missing features. Softshadows and Motionblur. So i gave it a little thought and came to the conclusion that you can easily achieve both of them if you take multiple subpictures per frame and randomize the lamp locations.
I build an example blend file (for 2.5.6) to test this and the overall result is pleasing. Only bad part is the integration into Blender itself (i obviously faked it). At first you have to slow down your animation and you will need some external software to blend the images together. This really slows down the overall progress.
Could it not be implemented in the OpenGL Rendering Feature, that it automatically takes multiple subframes, randomizes the lamp locations according to the given softness radius and blends them over each other? Would really help out as long softshadows aren’t included in Blender (game engine) itself.