Sony seem reluctant to talk about the details of how the consumer will purchase this service. By now if it was going to be part of Playstation Plus, Sony would be telling us. They'd be shouting it form the rooftops. To be fair, we get a very good deal already from PS+ and I can't see Sony giving anything else away. Lets remember, folks, Sony are a business, and they need to make money. There is a chance it'll be used as an instant demo delivery service for subscribers, but I can see a premium 'Spotify of Games' offering coming very soon.
If this is for games we already own, are we happy to be paying for them once again? What happens when publishers remove games suddenly as is their whim? I don't want to be 50 hours into Skyrim when suddenly it vanishes in a puff of electronic smoke. Netflix having been cleaning out the old content this January, so a precedent has already been set. I'm not sure I'm ready to reinvest.
On a side note, it does also mean we are already using the last Sony console ever. Playstation Now will certainly work on PS Vita TV, as a well as a raft of other devices. We could be entering a thin client paradise where Playstation games can be played on anything. For a price.