Since I first "Lived" in NYC as a summer school student at NYU - going to WHATEVER they are doing at the Delacorte has been on the top of my to-do list for every visit. The experience will be somewhere between two extremes, both good in their own way.
If the show is getting Rave reviews, seeing the show for free is a day long committment.
If the cast never gelled and the stage design is out shining the leads, drop by around 2 or 3 in the afternoon and they will probably still have tickets.
Either way you get to see theater with one or more TV or Movie stars in it and walk through part of the park at night while feeling fairly safe and all for $0.00!