Although Linux does turn your PS3 into a seemingly powerful pc, it's
worth noting that any of the games created by fans aren't as
spectacular as you may think because the PS3 is such a complex system
to program and its power lies in hordes of specialised chips rather
than one mega-processor.
Richard, that's only partly true. The PS3 and its cell processor is complex to programme, but a large part of the reason does lie in the processor.
Without wishing to get too technical, the cell processor is basically a power pc chip managing 8 other processors. These processors are intended to speed the graphics content of any programme, in the PS3 implementation anyway, while the power pc part acts as manager/director. This means that a programmer must allocate and keep track not just of the powerpc calls, but also that for each of the other processors, which is way more complex than, for example, the powerpc chip alone and its instruction set.
It's this that makes the PS3 complex, but also blindingly fast when correctly implemented. Also, SDKs are not that commonly available - IBM produces one, not sure about what else is available - which means the programmer must create routines normally handled by an SDK. That said, if you're using a PS3 you're also using virtually the same chip used in some of the worlds fastest supercomputers.