PS3 will save the world

Firstly I agree with the sentiment that some people are overhyping the cell and are talking it up without having any understanding of it, and it is sickening. (edit: but I do have to laugh at all the fanboys thinking that buy buying a PS3 they'll single-handedly rid the world of cancer)

Secondly, I've a degree in CompSci and have read up extensively about the cell, and am now going to explain why, through it's design it is very suited to Folding@Home and other medical/scientific uses (I don't actually know a lot about F@H but I can infer the types of calculations employed as I'll explain below). The Cell processor consists of a PowerPC based core (PPC) and 8 vector processor cores (PPEs, only 7 of which are active in the PS3). For now we can ignore the PPC, which is more or less the same as the x86 chip sitting in your PC and focus on the vertex based SPEs. Vector processors, such as the SPEs are specifically designed to carry out small sets of instructions on large sets of data, commonly know as vector operations. A common vector operation may be in a physics simulation to apply the force of gravity to a million seperate particles. A standard general purpose processor (PPC, x86 etc) would need to load the instruction (i.e. apply gravity) and load one piece of data (a particle) and carry out the instruction, then load the next instruction (which is actually the same thing again, apply gravity) and the data for the next particle and carry out the instruction, and so on for each of the million particles. A vector processor on the other hand will load up the same instruction (apply gravity) but will take a whole bunch of data (particles) and apply it to all of them. That's somewhat over simplified, but it explains the principle.

It also shows how/why physics is a vertex operation. With physics calculations being an important, as well as computationally intensive, part of many scientific apps it's clear that the cell has a huge advantage over your standard x86 processor. Ageia's physx processors are essentially vertex processors on an add-on card.

Graphics operations, such as translating a huge number of points/vertice around an axis, are also vector operations so naturally your GPU is also a vector processor (with some other stuff like shaders bolted on). With the talk of an ATi/GPU client being developed for F@H, I think we can safly assume that F@H mainly uses vector operations too, which explains why the cell can process it so well.

We should also remember that the cell wasn't just deisgned by Sony for the PS3. IBM and Toshiba have also played a role in it, and have plans for it, and it's currently being used in IBM servers, military simulations and medical imaging equiptment.

The wikipedia article on vector processors is worth a read.

As an irrelevant piece of trivia, video encoding/decoding is another vector op which is why some vector like instructions have been added to x86 (MMX, SSE etc).