I had a long discussion today about the premium areas with the manager responsible for them (among other things).
The Cabanas and upgrade chair/umbrella locations must be reserved at least one day in advance by calling 407-WDW-PLAY. Full payment is required at that time.
Same-day cancellations or no-shows do not get a refund.
If there is any availability on the day of use, they will be rented out on a first-come, first-served basis.
At TL, the High and Dry Towel Company now has a separate line for people who have pre-made reservations to pick up the towels, mugs, wristbands, etc. Anyone wanting a "day-of" has to wait in the regular service line.
Depending on season and other factors, the current maximum rices for a cabana is $300 and for the other reserved areas is $50. Also, if there is still availability at 2:00 the walk-up price drops to $175 (and still get all the benefits).
Although a reservation cannot be made for more than six people, if you have additional people they can be added for $25 each and will get the towels, mugs, etc. The number is not specified, but it depends if the group is all adult or if children are involved.
If the Park never opens, or closes within a few hours of opening, refunds will be given. For summer afternoon thunderstorms there will be no refunds (unless it is an afternoon rental, and then on a case-by-case basis depending on time rented and when the Park closes for the day).