I haven't played Now in a couple weeks, but I tried it a good bit during the closed beta. I came away with three major impressions:
1. The primary differentiator of how a game performs seems to be the game itself.
That is, some title were consistently better-looking and better-playing than others, even switching rapidly between them so that net conditions should've been about the same. Also, games seem to handle bad connections in different ways. Examples: DOA 5 would occasionally turn into Youtube-esque pixel soup, but no matter how bad the video got, I never felt any input lag. I played a bit in the training mode where the buttons you push are shown onscreen, and that display never felt unsynched. On the other hand, in Hunter Trophy America (or something) the video would stay good, but there'd be a big noticeable gap between button press and action. And Fuel would accept your input on time and react, but only drew a frame when it got a full one--so no bad compression, but a complete slideshow and unplayable at ~2fps sometimes.
2. For whatever reason, it seemed tough to maintain quality of connection.
That is, even the games that generally ran well would sometimes sputter and stagger. Was this due to local internet traffic? ISP problems? Distance to Sony's servers? The PS4's network card? No way to tell, but it definitely made me wary about committing too fully to a streaming future. That said, the third major impression was:
3. At its peak, streaming is excellent quality and has great potential.
A large chunk of DOA5 I played at 60fps with no impression of any video compression. (I'm not saying there wasn't any, just that perceptually it didn't stick out.) The version of Lumines on Now was apparently flawless the entire time. In these best-case scenarios, it really felt like playing off disc.
Wired 50/15.