Just applied this to La Liga and got a few good games in, playing on: Pro, zero speed, 15 minute halves.
It's definitely more realistic, and it even makes the game a bit tougher because you really have to manage how your own team pressures the ball. If you don't use the close down button well in conjunction with the 2nd teammate help button, the AI will have a better chance at retaining possession, since your AI teammates are all programmed to pressure less.
This tweak also doesn't seem to have any adverse effect on the backline, for both the user and the AI controlled teams. That is of course a good thing. I was thinking it might make the defenders too passive, but that's not the case.