There appears to be an improvement in the situation over the last few weeks. The biggest problem is stupid people just stopping in the lanes and flinging open doors and blocking traffic. If you follow the signs it will probably be ok. Good Luck!
I drop off/pick up at Malaga airport on average every 6 weeks and haven't encountered only one problem really.
The problem are the new barriers after the drop-off area. I think there is a time limit of 15mins after that you have to go and pay at the multi story carpark terminal and there are quite e few people who get caught out with the inevitable consequences. Its like a chain reaction as more drivers go over the time limit as they get stuck behind others. I got stuck behind a guy who had no money on him so I use the multi storey now.
The multi storey car park is the same building that the car rental companies use. Just follow the signs to the car rental companies and take the first entrance after the car rental one. The pay stations are on level 2 which is also the departure level. Make your way to the security end of the terminal and take the stair, escalator or lifts down to arrival hall.
Yes the 15 mins are free but not likely to be enough if you're picking somebody up.