I've been twice, it can be a great laugh, the first year game play was much better than the second. But the social side of it was better the second time. The team running it are great but there just aren't enough marshals to keep a good watch on the game, the site is huge and terrain varied enough to make things interesting. There are aspects of the day that are fun, when you can get away from the huge crowds and have some good quality firefights with likeminded opposition, but it wouldn't take much for someone who isn't feeling the spirit of the game to be a dick and ruin things, they are then hard to track and deal with just because of sheer numbers of people.
The first year I went with about 10 guys from the team, the second year there were about 15 or 20 of us. But there lay the problem. There were so many people there last year that game play suffered, it was hard getting involved in the objectives and taking the game play seriously.
I would say go at least once for the experience, where else will you see 1800 airsofters all playing together. If you like it go back again another year. Myself and many of our team are unlikely to go this year, we just didn't enjoy the gaming as much. But in the year between 13 and 14 we have moved away from mainstream blatfest skirmishing and towards Battlesim, Filmsim and soft Milsims.
Your questions about propane I believe relate to the fact that it isn't safe to use in guns (they claim), presumably it's because it isn't a propellant that the guns are actually tested or designed to use. Also I have heard mention of the inconsistency (again nothing to back this up) of propane and the fact it can sometimes make the guns hot (in terms of power). It may also have something to do with a fire risk or explosions.
They don't allow hot burning pyro, so that's smokes, flash bangs and other mainstream pyro out due to fire risk, most of the site is coniferous forest with lots of dead material, in the middle of summer its a tinderbox just waiting to go up. They claimed to have found fires there days after events. That's not to say there aren't huge bangs, they are just all marshal controlled.