USB 3.0 doesn't rely on polling either, so it's also better than USB 2.0. It has less CPU overhead as a result, and inherently less input lag, even when USB 2.0 is running at 1000hz. It does however still use a driver, so PS/2 is still more direct to the CPU, and therefore theoretically a more responsive interface. HOWEVER this is never the case in reality. Because it actually has slower throughput, it's slower and less responsive than USB 3.0 and even 1000hz USB 2.0 in practice. It's more noticeable on certain keyboard keys that transmit extra data, or multiple key presses, and it's infinitely slower than even USB 1.1 for mice, which I think use 100hz reporting rates in W7 anyway. I'm probably not using the correct terminology but this is the gist of it. PS/2 is also much less capable of delivering power. Without a doubt, USB 3.0 is the best current interface for KB and Mice, while usb 2.0 is second best (2.0 can even be programmed for NKRO). Will be some time before manufacturers bother with 3.0 though.
