Yep, it's free Ben & Jerry's mini cups, usually 2-3 flavors and then they will have the chocolate covered Cherry Garcia ice cream bars. But you really have to be in the right place at the right time, I think they only fill the bins twice a day. I'm not much of an ice cream person, except when it's hot, free, and at Bonnaroo.
I just want to know who's playing the party! There is such a good undercard that it could be anyone!
My take on the party is that it all depends on who is playing Thursday. You need to remember that a lot of VIP attendees will not know many Thursday bands, so the lines for the food and especially beer tend to be long. If you are debating missing the food for a band to see, go see the band and get yourself a Grilled Cheese or something. However, the private concert is really worth it even if you have a passing interest in who is playing. If you have no conflicts, go to the show. You can walk almost all the way to the front most of the time, there is no pushing, a lot of dancing, and at the rail, you can literally reach out and touch the band.
If you are conflicted about whether to attend the pre party or a regular show... I will offer to eat and drink your share of food/beer and report directly to you later on how the food tastes, how drunk I am ..etc