PlayStation Now has exceeded expectations. Not only will you be able to stream PS3 games on your PS4, you can stream PlayStation titles from any generation on any device.
PS4 has a share button that allows you to "instantly" stream gameplay and "instantly" upload gameplay clips.
Back in October 2010, OnLive opened to the public, announcing that the service will be free forever. OnLive introduced these ideas, and does them better. OnLive's controller had a button that allowed you to instantly capture and upload the last ten seconds of gameplay. And every time you launched the game, you were streaming live.
Why does OnLive do it better? On PS4, you stream to Twitch. There is a 10-15 second delay, so voice chatting with spectators is impossible. On OnLive there is a sub-second delay with gameplay streams and you can voice chat with your spectators live while you play the game. This is impossible on any other platform.
PlayStation Now looks promising, and if Gaikai is using NVIDIA's Grid technology, the latency and gameplay experience will be superior to what OnLive has right now. But when it comes to features and seamlessness, OnLive can't be beat. Everytime I hop on OnLive, I forget how amazing and seamless the social features are.