The fact that the OP even bothered to ask makes me a fan of them.
I always say dress for the theatre as how you feel for the occasion. That said, with theatre seats tightly packed, I'm not a fan of rubbing arms with someone in a tank top or legs with a short short. Or behind someone with a big hand or big hair. There used to be common sense, not so much anymore.
"Hey little girls, look at all the men in shiny shirts and no wives!" - Jackie Hoffman, Xanadu, 19 Feb 2008