4) So you get 175,000,000 flops/sec or 175MFLOPS = .175 GFLOPs
5) The RPi consumes about 1.5 watts.
6) Therefore, we get 116 MFLOPS/watt/second
In fact, the GPU in the Pi puts out 26,000,000,000 FLOPS ... yes, that's 26 GIGA-FLOPS! So, the actual efficiency is ~17.3 GFLOPS/watt/second.
That's why the Pi can render Quake 3 Arena scenes pretty much on-demand with very little lag only when a large number of players wind up in proximity in a scene (e.g., dozens). It can render about 40,000,000 Gouraud-shaded polygons per second, which puts it between an Original Flavor X-Box and an X-Box 360, which is somewhat below a Sony PS/3.
Now, that's nowhere near i7 levels of performance, so, the Pi is in no danger of putting Intel out of business for high-end clusters. However, these are single-core CPU-GPU and the ARM CPU is only running at 700 MHz (the GPU is actually running at a slower clock rate. It has parallel circuits whose sole purpose in life is to multiply a bunch of floating-point 3-D matrices simultaneously and send the result directly out of the HDMI port running at up to 1080p at 30 - 60 frames per second (you have to dedicate half the RAM to the GPU at boot time for the latter).
The best things in life aren't things ... but, a Pi comes pretty darned close!
"Education is not the filling of a pail, but the lighting of a fire." -- W.B. Yeats
In theory, theory & practice are the same - in practice, they aren't!!!