Had pretty much the same experience arriving back from amsterdam last month. Taking nearly one & half hours from getting off the plane to getting out of the car park in T1 arrivals. The delys of 30 mins or so at immigration were annoying yet understandable.
My girlfriend was there to collect us in arrivals paid for the ticket at the well hidden payment machine outside in the car park thus avoiding the big queues inside and home we go or so we thought. We were 5th in the queue for the barrier waiting patiently. 10 mins later we were still there by which time there was big queues for both barriers. This being caused because the people in front of us hadnt bother to pay for it!! Then the next car hadnt paid then the next and so on. In the end there was that many cars trying to get out they opened the 2 barriers so everyone could get out. which was just as well as no doubt our ticket would have expired. And even with the barriers up people were still stopping to put there tickets in the machine.
So as you can imagine it was a very frustrating to spend nearly and hour trying to get out the carpark when all i wanted to do was get home and go to bed.