It looks like Sony's claim of the Folding@Home client for the PS3 being super-optimized wasn't entirely bogus. With around 15,000 connected units, the PlayStation 3's Cell processor is putting comparable Windows machines to shame, with more than double the processing power in only 1/10 the number of processors participating. While it still falls far short ATI's extremely impressive optimization, it isn't anything to shrug at:

According to the most recent Folding@home client statistics sorted by operating system, the PlayStation 3 leads all other platforms by a huge margin. The PS3 has 367 current TFLOPS, while the next closest is Windows with 151 TFLOPS and more than ten times more CPUs.
The article lists some statistics regarding this. There are around 160,000 “participating” CPUs in the Windows world, compared to about 25,000 for Linux and 10,000 for Macs. Now, if only Sony can optimize future games for the new console to this degree as well...