It's a shame but no surprise. The Aer Lingus return cost of checking in one bag is now €24 whereas Ryanair is €20 however Ryanair also charge to use check in desks which is unavoidable if you have a bag to check in and that is €10 return making the total €30 for one bag return!
Rumours going around that Aer Lingus are about to announce these new routes from Belfast:
Lanzarote - already bookable on aerlingus.com from September 30th
Milan
Munich
Schedule improvements for LHR also rumoured.