We used Tiffany in October, at the recommendation of the nice folks here on the DIS. Couldn't be nicer -- $95 round trip, and they were waiting exactly when and where they stated they would be. Very clean cars both ways, friendly drivers too. We even had to change our arrival time, since our connection was cancelled and they were still waiting even though they didn't know exactly when we were coming in.
I've never used Murray Hill, but I did see a negative post about them on this board tonight. They sent a vehicle that was too small to seat all the passengers and their luggage. But that's all I have heard so far.