Played a bit of everything for almost 2 hours this evening, and except for two 1 second stutters,the experience was flawless, tried VF5, MKX and Shatter to check latency and was almost indistinguishable from local gameplay. Then tried Motorstorm, that played great, and a bit of KZ:SF that also felt perfect (hadn't played it before so can't really compare with this one).
I'm genuinely surprised, i expected at least a little latency, especially when playing fighting games or Shatter, but i couldn't notice it. If the beta is any indication on future performance, people can really consider psnow a serious contender as a streaming service (many people say it plays bad, but it doesn't, really)
They should allow a streaming option for ps plus games if confident enough to make non believers change their mind.
As for the service, catalog is okay, nothing mind-blowing, some great games i already played, so not for me right now, but it really will depend on pricing. It has potential though and it really seems Sony has been doing their homework and is slowly putting everything ready for ps5 here.
Btw, games you played (streaming)are automatically added to PS4 menu as if you owned them, so it is quite convenient , since you do not need to go to psnow and search for them to play again.