Online Travel Booking and Bidding Agencies - Any "gotcha's" with booking through Expedia?

I am looking to book a vacation package (Air + hotel) through Expedia, versus going directly with the airline (Hawaiian Air) and hotel.

The package is about $200 cheaper than booking directly / separately.

Other than having to pay everything up front, including the hotel, are there any gotcha's or downsides to using Expedia?

Only the usual pass-the-bucking / responsibility-ducking if anything goes wrong. Expedia's phone reps are uniformly incoherent and mostly incompetent. And if you actually succeed in prying one out of them, Expedia is notoriously slow with refunds -- three or four billing cycles is the reported norm -- so if you're paying for a package in full, up front, sight unseen, bear in mind that your resource options are pretty much all slow and agonizing should you be dissatisfied.