I received a promo email offering a $50 voucher if I sign up for Discount Den. There are tons of $20 (and less) flights out of MCO, and I can take short trips with nothing but a personal item, so I'm considering signing up and taking a ton of weekend trips in the coming year.

As a Frontier newbie, are there gotchas and unexpected fees that would negate the $50 voucher or make the offer not really worth it? I don't want to sign up then end up paying more than I would have to fly my normal preferred carriers.