I attended all the guest Q&A's except for Julie Cobb/Rosemary Morgan, which cost extra.
Adam Nimoy, Leonard's son
Garrett Wang, who was not an official Vul-con guest but shows up almost every year (Voyager)
I found the Q&A's illuminating. Some of the actors didn't like their colleagues. Some didn't like the way the writers treated their characters. Some seemed to be acting, not being all that genuine ("actor's gonna act"). Some seemed to be real people. Well worth the money.