I love the disguises. I usually have my aliens wear their human suits. Mostly because I'm playing take over the world or infiltrate and pass on their genes kind of storylines with them.
I wish they weren't discovered so easily though. I actually wish they would never be discovered unless they chose to reveal themselves because it's kind of irritating when it happens and doesn't happen in a way that helps or hurts my world domination story lines.. it's just an irritant mostly, so if they took that discovery away completely I wouldn't mind.