The way I see this playing out is that it's a huge resort guest perk and more than meets the eye. First off, you could actually get 5 LL selections in advance (counting your two individual selections). So, once resort guests get through with making their selections 4-7 days before their visit, it's safe to say that the very, very popular attractions are going to be the ones with thin or no inventory (Tiana, Slinky, Rat, Space, etc.).
At that point what day ticket guest or AP is going to buy the service if they can't even gain access to a single headliner or E-ticket attraction? I don't think very many quite honestly. The result should be very healthy inventory for resort guests' 4th, 5th, 6th selection (Pirates, Peter Pan, etc).
Remember, you have to make your attraction selection before purchasing -- most APs and day ticket guests will balk at the remaining availability.
Resort guests should be able to basically ride anything they want, without a long wait, every single day, if they're willing to pay.