It always amazes me to find people in the greek system that still call them "frats". We were taught on our first day about how that is considered disrespectful.
Anyway, I am in Pi Kappa Alpha at Drexel. The experience has been almost all positive. The only negatives are dues, but even they come back to you, for example, we have two formals a year, a dance hall, open bar, transportation, etc, and we only pay $30/person, $60/couple. We also get a beach house for a week in the summer, all we have to pay is $20 additional, and that covers the house, food, etc. Not a bad deal. The other negative is the stereotype you have to deal with...people outside the fraternity system tend to think we're all assholes who do nothing but drink and rape girls.