No thanks. I have done both, Manhattan and downtown Chicago. It really depends on the time of day. The last thing I want to do after a redeye or a 4 leg day is to sit in a smelly van with a driver who enjoys giving you whiplash in traffic.
Most of the time the van at most of our destinations isn't on time and then factor in the drive and it can be 1-2 hours before you even check in and finally get to take that dump you have been pinching all day.