Hi!
We were there for 10 days over New Years. We used some shuttles and took taxis some.
We did not use the Universal shuttle because it left after the park was open and we wanted to get there early. Also, we were ready to go back to hotel before the shuttle.
We did use Disney shuttle which worked ok. The only thing we didn't like was that it took 45-50 min. to RETURN from Magic Kingdom.(only did that once!)
One time we took the monorail (with the kids riding upfront!) from Magic Kingdom to Epcot and then took a taxi to hotel for $10.
The taxis contracted to Nick cost $4-5 more than other taxis. So I would suggest calling your own cab.
Also, to catch the shuttle from parks you have to go to the chartered bus lots and stand at the lane # for your bus. And don't be late! The drivers aren't there more than a minute or two before leaving!
Jama