Right now, I play all free games. I'd play the paid ones (or, at least one every so often) if I could guarantee that I didn't have to pay for the routes after I paid for the game in the first place. I've done that - paid for a game and then was expected to pay for all but 2routes available. :\
Oh, and this one is right up my alley, so I'd definitely consider paying that one-time fee to play this one.