Folks:
This technique has been used by snooker players for decades. It's called the "rear-fingered" grip.
Here's an example -- at 8:00 minutes into the Ronnie O'Sullivan vs. Chia-Ching Wu in the World Pool Masters (this link will go right to that spot when you click on it):
http://youtube.com/watch?v=W2Ye61WiLMk#t=8m
(Watch Ronnie's grip hand very closely in this outtake. You can see how the "pincer fingers" -- i.e. the forefinger and the thumb -- are completely loose and relaxed, while the cradle fingers -- the middle/ring/pinkie -- are cradling the cue.)
Additionally, think of it this way -- when you grip the cue like this, you are more emulating the way you throw a dart or a javelin, but in an underhanded fashion. That is, the leading fingers "fly outward and away" like a sabot, with the rear fingers being the ones to support the throwing implement until the last possible moment. In the case of throwing a dart or a javelin, because you're throwing it overhanded, your ring and pinkie are the sabot, and "fly outward and away" as you go through your stroke, with the "rear fingers" (the pincer fingers in this case, the forefinger and thumb) being the last to release contact from the throwing implement.
This is reversed for delivering a cue, because you're delivering it underhanded, not overhanded. Thus, the rear fingers are the ring and pinkie -- the thumb/index/middle are your sabot.
Fran is right, in that you don't have to exaggerate the movement with the "sabot" fingers opening up and flying away. It's sufficient to just feel the thumb and those first fingers release pressure from the cue, with the fulcrum in your hand being the ring and pinkie fingers that the cue rests on.
It's a very effective, time-tested, and proven technique.
-Sean