I recently flew to a fairly busy UK airport, one I used to be very familiar with, but which I had not been scheduled to for a couple of years. We landed, taxied in and parked on the stand, using the stop line on my left to judge our stopping position. All appeared normal, the ground crew approached the aircraft, steps were positioned, doors opened, passengers disembarked until there was a slight knock on the flight deck door. Stood there was a very nice gentleman who introduced himself as the marshaller, asking us if we were aware that we needed his help to park the aircraft. Well, now we were!
For years this was a self parking airport so when we arrived at the stand I just assumed that that was still the case. There was nothing indicating the contrary, the stop line was still there, painted on the ground, and since no marshaller was in sight at the time I just pulled up and parked like I had done countless of times in the past. Moral of the story? I refer back to B2N2's post: it all depends.
Usually it's quite clear what the marshaller wants from us and wat we want from the marshaller. The only slight issues that come to mind are the marshallers who want to oversteer an A319 onto the stand as if it's an A340-600, those who abruptly and without any prior 'hint' give the stop sign, and those who seem to marshal 'in reverse'.
Question for the 'batsmen': why do some marshallers walk backwards and sideways as we approach to parking position?