From my interview group 12 interviewed 5 got hired. Of the 5 that got hired none of us wore ties. Some of the one's that didn't get hired were wearing tie's and one was a little too casual (trust me when I say toooo casual). I felt weird not wearing a suit but hey business casual means to me no tie. With that said what you wear is a small part of what they look at and this is not a f'in GQ convention. We have a bunch of gubers here and they got hired. Just be positive in your attitude, wear a smile, and try not to be joker or center of attention during the interview. Take it for what it's worth.