I've done it several ways. I've had a car service and I've taken the Mears shuttle. The Mears shuttle is about $36 r/t pp. It does take a bit of time because it will stop at off-site resorts along the way. But, it was nice to see areas of Orlando I wouldn't normally see. It took me about 90 mins from arriving at the Mears counter to the Dolphin!
A car service will run about $130, plus tip. It's quicker, and can be cheaper depending on how many people are in the group.