How reliable are these services and how hard are they to use? My wife is hesitant on using these services. Some of her questions if you pay round trip do you get a voucher to use on the return trip to the airport? Has anyone used the grocery store run and how did it go? How much do you tip the driver? Will this be cheaper than a rental car? Why I ask this is we are going to be at the Dolphin so we have to pay 6 nights of parking, so would the rental car and parking fee be cheaper than the Town Car Service? Last year trip we had a rental car for 6 days and basically it sat the whole week, One day we used it to go to Outlet shopping and Downtown Disney and the other time was we had to make a emergency diaper run at Crossings. I just don't see spending the money on something we hardly used. I would appreciate any feedback on any of these questions and thanks. 
