I use Air Asia from time to time for s/h trips around South East Asia. They used to have free seating (the European scramble for seats is tame compared to what I've experienced over there!). They have recently moved over to assigned seating. Basically, you either pay to choose a seat (they charge extra for the premium seats- front, emergency exit etc..) or you get randomly assigned one at check in. Clever little money earner (Easy and Ryanair take note!).
The only problem is that it boarding takes longer than it used to. People no longer feel the need to queue at the gate an hour before departure then run as fast as they can to the plane. Thats a big problem for a loco doing quick turnarounds- more chance of delays, less chance to make up for delays etc...
Ultimately I think its a chouice between the lesser of two evils. Do you want the comfort of assigned seating or an increased chance that your flight will be delayed?