What I can't stand are interfaces that have been dumbed down to the point that every option exists as a bazillion buttons to sort through. Or every option requires some sort of dialog confirming each action. Take a look at ICQ 98 and then at its bloated son, ICQ 2000b, and you'll get an idea of my ultimate pain. Luckily, Mirabilis/AOL had enough sense to allow the users to do pretty extreme customizations, assuming you can figure out where the hell the preferences button is hiding.
I stumbled across a website today that attempts to educate its readers on what is and is not an acceptable way to approach your interface and dialog boxes. The very well named Interface Hall of Shame is sure to enterain any soul. It will also prove to be therapy to the souls of us poor technicians. It reaffirms clearly that our pain is not felt alone.
Of course, after seeing the rampant stupidity housed there, I have to wonder: who causes me the most hair loss, end users or programmers? After reading that site, I would have to say the programmers. Not sure what I mean? See for yourself.