Try this: Open System Preferences, Power Saver, and on the CPU slider, move it to Never. The screen will still go black after the time set for that, but the CPU will stay on continuously. Now when you tap any key, all that has to happen is the screen wakes up. What is happening now is the CPU has to wake up, reestablish where it was, fire up the drives and recover the system state from the drive. That's what is taking the time. By never letting the CPU sleep, you are avoiding that process. However, the CPU will be running, consuming power and theoretically wearing itself out. It's your call on whether that is more important to you than having to wait a bit on wakeup.