I played in this event the last time it was held at Oakmont, which if I'm not mistaken was in 2007, the same year Angel Cabrera won the Open there.
The event that year was held in late October and conditions were SUPERB. It wasn't $1000.00 to play in '07 but you do get to play whichever format you prefer and for that kind of money, you'll obviously want to play your own ball, which isn't a problem. I know there were a number of GCAers in attendance and I played with one but I don't recall bumping into anyone else in person - at that time, I was brand new to this site and likely was a bit on the shy side.
A bummer was the fact that I couldn't use the tax deduction as a resident of Canada but if you have the means, it's a great charity you're supporting, the golf course is one of the world's best and the event itself is first-class.