Transfer to Key West from Miami was no problem. I phoned 2 days before my return trip but when I arrived neither bus had me rostered on it and both were full. One of the guides was really helpful and she was willing to sit on the steps for me to have a seat but in the end 2 people didn't turn back up for the return trip so we both had seats. Grey line seems to source out a lot of their trips and communication could be greatly improved between them and the other companies.
Everything was on time and on plan. The guide was very friendly and informative. You see a lot more from a bus than from a car and you don't have to pay for parking. Well worth the money.