I've used GG once when we were staying at the Boardwalk Inn without a car. It was nice to have a few snacks, breakfast items, drinks, and a bit of wine and beer delivered. I liked the convenience of it, but it isn't my normal way to do our snack shopping.
All our other trips, I've had a car and stopped at Publix or Super Target, or a few times we've had a town car with a stop.
I was debating the same thing for our upcoming trip. We have a car, but don't land until 4:30, so by the time we get on the road with our luggage, I may not feel like stopping at the store. Now, we're going for 15 nights, so we have plenty of time (and we're staying in condos, one move halfway through) so we will cook a lot. I just thought maybe I'd order a few things to get us started, so I wouldn't have to shop the first day.
When I looked at the prices, $8 a case for water, I decided I don't mind stopping somewhere quickly for a few things myself!
No Trader Joe's in Orlando. I think there is a Whole Foods near Sea World. We stayed at Marriott's Harbor Lake, which is super close to Sea World, and I recall a Publix being close to us.