Guests of the S/D can attend E-Nights and use Early Entry and resort package delivery. The only thing you cannot do is charge back to room from the parks using your S/D room key. Other then that everything else is pretty much the same. Actually there are a couple of things we like better.
1. You can request housekeeping to clean your room at a certain time everyday.
2. You can check your charges to the room daily using your TV.