I was considering them, too, but looked around on their site and couldn't find how to cancel a reservation on-line. I found a link in their FAQ, but it was a bad link. I emailed them to ask about how to cancel if needed, and this was their response:
Please be advised that cancellation policies may vary between properties, so be sure to click on VIEW DETAILS next to name of the resort you want to book and go to the bottom of the pop up page to view the specific policy. You can just email us as you have here to tell us you wish to cancel your booking, as our emails have a whole staff that monitors the emails all the time, or you can call us toll free in the US at 888-579-1054 to tell us you wish to cancel. if you leave a message on our machine during closed hours we can take the cancellation that way too and email you confirmation that we have cancelled it @ refunded your credit card.
It looked like it would be OK, but I really prefer to be able to do a cancellation on-line myself. I ended up going with Priceline instead for that trip.