Ryaniair have been operating a 'priority boarding card' system for a while and seems to help them get pax on in a more organised fashion. Think it applies to the first 90 or so pax that turn up to check in. Doesn't quite give you the seat you want but does encourage some people to check in a little earlier and report to the gate on time. Ryanair and Southwest have been doing it sucessfully for years and are probably the two most sucessful LCCs!