Yes several times as a visitor to Melbourne, didn't know to ask for a return ticket ( cheaper) the first me. Also no advertising anywhere obvious -like the airport! where you board that it is an express - no stopping to city and that it ends inside the Sothern Cross railway 'complex'...which is great and that you can catch V Line trains, regular trains or trams into city. They don't mention either that there is a free shuttle bus included in your ticket price. Just get off bus and then they direct you to office in front of bus where they arrange shuttle. There is 7-11 right there too and if you across into station ...more shops, fast food, Grill'd, Woolworths and much more...coffee club is above the bus station with heaps discount/clearance shops.
So all you see when you first get to airport is a ticket booth outside airport entrance and red skybus...but you don't know where it goes, how it works etc! Advertising much needed!!! Because it's a great fast service ...25 mins airport to city direct and plenty of luggage area.
Actually only once, since I live out in the suburbs. I have to take a train into the city and then the skybus. However, my experience on the Skybus was great. It was on time and the service was excellent.