Great Question, Marco.
First and foremost I would like to spend time meeting and chatting with fellow enthusiasts. Playing pinballs I've never seen or played would be high on my list as well - Especially if collectors brought games such as 60's EMs and System80s. Checking Gavin's Stall would be a thrill, as I could check out the handiwork of a playfield or two. If Coconut Island was onsite, I would play that for a while and talk "shop" with Nug & Nick. I'd make coffee for MarkC's Stall so he does not lose customers, and I'd check out other pinballs stalls.. The Auction would be interesting - They always are !
Best part of all would be a beer with guys on the forum