Why does all of this matter? Performance, pure and simple. In my tests, Core 2 Duo computers outperform Core Duo computers on tasks across the board, from rendering graphics and video to spell-checking documents. The speed improvement varies widely, but on average it's about 30 percent. That's significant in an industry that thrives on tiny, incremental improvement. Better yet, there's not an appreciable difference in battery life on notebooks, as power consumption for both chips (at the same clock speed) is about the same.