Used to fly in and out of MEL nearly weekly and never had issues with the drives. Traffic can be awful in the mornings but only once or twice was the driver a couple of minutes late. Once they sent an old piece of substance (car that is, the drivers was ok) but overall the service is very dependable.
If you want a van or a minivan they will charge extra. But the regular Holden can easily fit a golf bag in the trunk.