We've been sampling the Share Play feature that launched today on PlayStation 4 as part of the 2.0 update and we must say we're impressed by it so far. We've passed the controller across Europe, and played co-operatively in Pix the Cat. There is some input lag, but not more so than what you can easily get adjusted to in most games (though we assume fighting games may be difficult to play this way). But as the feature is essentially the equivalent of giving someone else the controller - there is also potential disasters lurking for those who trust untrustworthy friends with their games. We managed to delete save files off eachother's PlayStation 4 units (in-game), and while you won't be able to access a friend's console menus there's enough damage that can be done in a few seconds. Of course, if you still want to share your game with an untrustworthy friend you can always upload your save files to the cloud prior to letting them loose, but we're curious as to how files that are stored server side like in Destiny and FIFA 15's FUT work with this system. Of course, if you spot your friend being up to no good you can instantly take the controller back from them.
Share Play is limited to one hour at a time, and you need to be a PS Plus member in order to play someone else's game.