It seems like most of the f2p games on psn are free game trials. It's kinda lame that they pass a trial off as a f2p, at least DUST got it right.
SOME of the f2p games on the PSN ARE free game trials. Uncharted 3 MP edition (level cap 15?), MAG (level cap 8?), etc.
Dust 514, Free Realms and DCUO are the only true f2p multiplayer games currently on the PSN. The only thing you unlock by paying through a subscription for Free Realms and DCUO is access to earning trophies and some optional features. They are completely free to play otherwise.