We valet parked the whole week we were there last month. The walk to the lot isn't bad, but it sure was nice to have the car waiting for us when we walked out the front doors--nice and cool with the A/C running, since it was 90's most days. We never actually drove to theme parks (the buses were great) but used it to go to DTD a couple times, both waterparks, other resorts (Poly & BC) and Discovery Cove. The system is set up so you can't be charged more than once per night so going to other resorts is no additional charge, that's what we were told and it was correct for us, but we checked @ check-out to be sure. For the week, it was $70 + tip, so compared to all we were already spending, I considered it a great deal and a nice treat. It took convincing at first, but even DH was happy we valeted.
HTH