Waitable-timer resolution is the same as the system timer resolution.
Do the he said what??
A waitable timer as as accurate as any other event, which is nearly down to the microsecond.Though of course no guarantees.
Well, I don't think Microsoft broke it's terse power-saving rules just to make this specific type of timer more responsive... Then again, I never used it, but I have used an tested (against QPC) most of the other thread-sync events, and they all ran at approximately the system-timer resolution (15ms by default). I then also found some articles that mentioned this - can't remember where, so I don't think I am mistaken about waitable timers, really. But I'd be more than happy to be proved wrong.
A waitable timer makes the waiting thread ready and higher priority at the exact time the time is up.
That doesn't help much, for two reasons:
1) Most games already use the highest process&thread prioritiy available
2) The thread becomes active between intervals of the system timer - you can only hope that it becomes active sooner than later.