For decades everyone was spoiled by Moore's law directly translating into an exponential speed increase, the CPU clock was going up exponentially to 3GHz which was reached in 2003, but in the last 5 years it seems to be stuck at that point. Instead, manufacturers try to pack multiple cores into a chip. People started to look for alternative ways to get faster computation (see MRSC 2008 conf.): Field Programmable Gate Arrays (FPGA), General Purpose computing on Graphics Processing Units (GPGPU) and most recently the Cell Broadband Engine (Cell/B.E.) from IBM-Sony-Toshiba.
Tony Williams over at the ChemConnector Blog has had a couple of people ask him for comments about which way to go and which one is better for a particular application. The writer of this article, though, just invested two man years of effort porting to the Cell/B.E. and not only does he have strong opinions he also have enough "hands-on experience" to comment.