Innumerable times--but again only if I am the shooter. Saved many a cold night with that move. On the other hand, I never get lucky with the "royal at the buzzer" like Rob does. And certainly the odds of hitting 2 nines are far less than getting a royal.
I am prepared to lose my entire buy in, but I feel that on a cold game when down to my last 300 I am not going to sit there and grind my way back. So it's either take the $300 (which I do most times) and walk away, or take the one shot. The one shot has served me way better than trying to grind my way back. Of course, taking the 300 and walking away is more prudent. But in my game, 300 is somewhat meaningless.