My next questions would be 1) what is the refund policy for Priceline? And 2) do you pay all upfront or just a one night deposit? If you book directly on the Universal website, you can cancel up to 5 days before your trip and receive a full refund. Would Priceline have a similar refund policy?
Also, have you checked the prices for Portofino Bay Hotel and Royal Pacific Hotel? Those two hotels also have the Unlimited Express Pass for length of stay, and are worth considering, especially if their rates are lower.