This, above all. I could have forgiven some of the event's other flaws had the house lineup been stellar... and it wasn't. 2011 had the best house lineup hands down in the years I've attended... 2010 had the worst. (IMO 2012 isn't impressive at all, either, but House of Horrors & Gothic & Dead End are all better than 2010's efforts).
All IMO:
Psychoscareapy was a misguided bore
Legendary Truth was a good effort but forgot to actually have a plot, decent costumes, and generally be scary
Hades just underwhelmed with too many missed opportunities
Zombiegeddon felt generic and while I liked ZAP it just never really gelled
Orfanage I actually liked a lot for the atmosphere & casts, but it could've (and should've) been even better
Catacombs was rock solid
HAVOC had great casts but the house itself was poor
Hallow'd Past = one giant missed opportunity, though a handful of fun scenes