I've been to a few underground psy parties held in semi-squats, advertized solely by word-of-mouth or by flyers that are handed out at other psy parties, and I have to say psytrance is one of the biggest druggie genres out there. The only time I've actually seen someone shoot up in public was at such a party. Trust me, there may be alot of goaheads who only smoke weed/take psychs but they bring in a shit ton of hard drugs on the side. Even 'trashy' drugs such as booze, amps, coke or opiates, though it's usually teenagers who are into shit.
I'm talking about the Belgian (Flemish) scene here, which is all about oldschool.
Really depends on the party though. Some psy parties are jammed with hardcore druggies, fuck-ups, people skipping school on thursday to catch a party on wednesday evening, people selling drugs, etc... And other times it's the other way around, you see lots of "real" psy people, lots of "travel agents", no hard drugs in sight, and you seem to recognize almost everyone.
The best parties are the ones with fewer than 200 people. :D