You're too early to see any availability yet for summer of '08. We're Marriott owners (besides
DVC) and we can't reserve our Marriott week until 12 months out. If you own two consecutive weeks with Marriott, you can book at 13 months out. Think of it kind of like DVC's 11 month window for reservations. Plus, I would imagine not all Marriott owners book at their 12/13 month window. Some people probably wait (just like DVC).
I think you'll get a studio pretty easily. A 1 bedroom would be tougher.