OK, here's a contrary opinion. I'm a platinum member in the Marriott Rewards program and also eligible for the government. I had such a bad stay at the JW in Orlando that I will never go back.
The grounds are indeed beautiful, and being so new everything is in tip-top condition. It is certainly less convenient than staying right on property, but to some people even that's a bonus to kind of "get away" from the hustle and bustle of Disney each evening.
My bad experience had to do with staff attitudes. There was a problem with my room type that never got resolved even after talking to three different front desk people and four managers over the span of three days. They also messed up my parking charge (it was on the room bill but the guy at the gate wanted to charge me again for the whole length of stay, and it took--get this--OVER AN HOUR for him to keep calling back to the hotel trying to figure out what to do. The whole time we're sitting there in the rental car watching our flight time get closer and closer...
I wrote a letter to the GM explaining in more detail than I've used here what happened and how I felt they could have handled things better. I never got a response at all. While I expect some hiccups at a brand new property, I cannot tolerate poor guest service and then even ignoring guest inquiries.
My advice is to avoid the JW Marriott and stay on property.