Sony has been trying to figure out ways to make subscribing to PlayStation Network Plus attractive to PlayStation 3 owners.
They have come up with one deal in which PSN+ users may download the M.A.G. client for free, and allow them to engage in multiplayer play up til level 8. However, all of the XP earned beyond that is not forgotten, and unlocks once the player chooses to purchase the full game for $29.99 USD.
This is not unlike many free-to-play MMOs, though it remains to be seen whether this will be a good enough reason to subscribe to PSN+.