In speaking with TenTonHammer, Turbine's Adam Mersky has revealed that revenue from The Lords of the Rings Online (LOTRO) has tripled since the switch from a monthly subscription model to a free-to-play model was made.
It's not the 500% increase Turbine saw with Dungeons & Dragons Online as that game switched, but then again LOTRO was more popular to start with. Turbine also mentioned that they are seeing a lot of new players coming into the game and that the world feels "alive and vibrant".