PS4 and PC
Here's my impressions from another thread:
Finally signed up for the 7 day free trial and spent a few hours jumping around various games to test the streaming. So far no noticeable lag and not a single stutter. I ran some tests with Red Dead, Sonic Generations, Motorstorm Apocalypse, Street Fighter 2, Comix Zone and Gravity Rush. Other than the graphics downgrade by the stream being 720p it was perfect. Controls were very snappy and I was intentionally trying to dart about quickly to try and create a situation where I might notice some lag.
My internet connection is gigabit download with 30 megabit upload and I'm in Toronto. Gonna play around a lot more once I finish off replaying TLOU but so far I'm impressed! If they can get the streaming quality to 1080p then I think it'll be perfect.
So yeah, with my experience so far there was no perceivable lag. It did feel like I was playing the game locally on the console, it's just the 720p resolution that gives it away. I imagine we'll be seeing some upgrades to the service before the PS5 hits.