
Re: what do you like best and hate most about festivals?
If it's large enough to require port-o-lets, please be sure that:
A) there are enough of them
B) they are kept reasonably clean
Seriously: Service them once a day -or more often- if the crowds require it.
Chairs are great(!), but there should be a chair-free zone in front of every major stage.
Please ensure adequate food & beverage is available. This could be the hardest part to predict in advance. But: No one wants to waste time in (any) line while their favorite band is raging.
As an example: At the Terrapin Family Reunion in 2002, the venue (Alpine Valley) ran out of bottled water late on the first day... Really!?! Are you freakin' kidding me!?.

... Plus: Despite the fact that we were
not allowed to bring in food or water, the line to get a grilled cheese was over an hour long. Really?! Are you frickin'... Well, yall get the idea: Grrr!
Please, make it easy (and sanitary) for us custy's to get our victuals on... and out!
At that wonderful venue the SOS, we typically eat every meal but one at camp. Why? We kinda like our own cooking. . . But we make sure to patronize the food vendors at least once per Fest - especially when the Sugar Shack is on site.
I may have more love/hate ideas later on - but these stand out for me as the real 'buzz kills'. . .