the biggest problem with the dual cores was the early ones where only 1.6+ ghz and as most if not all software written to date can only use 1 core it was basically like having two shit slow pc's running together, compared to a single core 3ghz+ p4, but now the duals are going up in clock speeds and with the new style stepping allowing for some very high clocks all of a sudden the new dual cores can run multiple programs at the same speeds as the original single cores

the new quads just takes things to another level.