We just got back last night & also rented from National using the Emerald Aisle. We picked a brand new Grand Caravan and had it for 10 days for a grand total of $156.00.
I signed up for the Emerald Aisle using the code for free membership on Mousesavers and used the Entertainmemt coupon. When we got to the garage at MCO, we had our choice of every kind of vehicle..........minivans, PT Cruisers, SUVs, sedans, hatchbacks, you name it! We took the Grand Caravan (over DD & DS's objections) because that's what I drive at home & was familiar with it.
If you want to take the chance when you arrive, this might be the way to go.