We stayed at GF and used taxis several times and we used a taxi to go to the Board Walk Villas to have a look around. I think though that most disney hotels are linked by their transport system so many people would question the need. We were pressed for time and I've got an account through work with Meers (i think thats the name) so thats why we used them.
P.S if you have got kids and want to use child seats in taxis it is always a gamble if the taxis have them