Picked up the PS4 disc copy for $20 recently, and just sat down to play through it. Credits rolled after a mere 77 minutes, and I was not hurrying. That said, I'm only at 7% completion, so I probably won't feel ripped off in the end.
The game looks great at 1080p/60. My biggest beef is with the controls, which are aggressively non-standard (triangle to pull up from a ledge and X to drop? WTF?), especially coming off a lot of hours of Splinter Cell: Blacklist. It also seems odd that this game would be so closely tied to the events of Peace Walker, which was until recently a PSP exclusive. Having only played the numbered entries in the series, I had no idea who Paz and Chico were and why I should care.
I like the potential of open-world stealth, and the experience here has me very interested in The Phantom Pain, though Ground Zeroes does feel like Konami decided to monetize a demo, which isn't very cool. Oh well.