Deafulting to fbo is good, but it should be more good to leave also prior working support for backbuffer on older cards who not have EXT_framebuffer_object. Reverting to "OffscreenRenderingMode"="backbuffer" is not working as expected for me on r200 Mesa/DRI drivers, for example in Max Payne 2 which now can't be even starting with backbuffer, Rayman 2 and Dungen Siege 2 also. In 1.1.22>= they worked.