One of the possible benefits that I can see with PSN is how it can be a potential way to increase customer loyalty when transitioning into the next generation. If Sony can find a way to reward current PS3 owners to support their next console (e.g., access to their current PSN library on their PS4, rewards for plus members, etc.), as well as continue to not penalize those unable to afford subscriptions (i.e., online play remains free), they may be able to hold onto more of their fanbase than they did in the previous generation, even if their competitors launch first.
Obviously Xbox Live gives Microsoft a similar position, and I personally will be watching the next few months to see how Microsoft and Sony utilize their subscription and user strategies.