The energy was very good, partially because it was filled with industry professionals who know the work that go into a production, and partially because there was an open bar from about 11 to 11:45. Lots of laughter, a bit more applause as each actor came out than I saw at a regular production a few weeks back. Some nice mingling opportunities (I was in line for the drinks with some cast members from Come From Away).
The people sitting next to me worked for out-of-town houses, and were grateful that they get to see a play (they only see musicals while in town).
I've already told someone from the Actor's Fund that they should try to do this every year.