Optical mice can work on a surface without a mouse, but to truly achieve the full control and accuracy of the mouse, you need a surface that is designed to provide the best results. Thus the high-performance mouse pad.
And if you've never used one, really used one, you don't know what you're talking about. It's night and day.
Yeah, it is like day and night. I just finished playing some HL2 and I had to turn the (In game mouse sensitivity way down from what I had it on with my old mouse.) I was all over the place - lol... But, now i've got both (game & razer) settings perfect.