Prime Nouveau
eric@gensokyo:~$ DRI_PRIME=1 glxspheres
Polygons in scene: 62464
Visual ID of window: 0xf0
Context is Direct
OpenGL Renderer: Gallium 0.4 on NVC3
157.687749 frames/sec - 175.979528 Mpixels/sec
168.748184 frames/sec - 188.322973 Mpixels/sec
162.604838 frames/sec - 181.466999 Mpixels/sec
162.187192 frames/sec - 181.000906 Mpixels/sec

Bumblebee Nvidia
eric@gensokyo:~$ optirun glxspheres
Polygons in scene: 62464
Visual ID of window: 0x21
Context is Direct
OpenGL Renderer: GeForce GT 555M/PCIe/SSE2
89.406007 frames/sec - 99.777104 Mpixels/sec
90.693321 frames/sec - 101.213747 Mpixels/sec
92.742092 frames/sec - 103.500175 Mpixels/sec
92.997387 frames/sec - 103.785084 Mpixels/sec