Played the second half of my season with this tactic. I did use unstoppable when I was at home and heavy favorites and I won every time I used it. I'm going to keep the tactic around because I think it's important to switch formations every now and then.
My comments about this tactic:
1) The striker sometimes went many games without scoring, and frequently had very low ratings around sub time in the second half.
2) There are many times where players will give away possession cheaply. One of the biggest things that happens is that due to the players all being close together, that means the other team's defenders are close together, and so usually a midfielder sends a medium length pass forward and if the first touch is not absolutely perfect, you will lose the ball.
3) It is very important to have good crossers at DL,DR, and the MCR, MCL positions, and good aerial players in the DLF and SS positions. They will get alot of chances this way.
I think in 14.3 that players like SS and MCA are less likely to end up running free behind the defense, and so there are many times with this tactic that if you're up against a good team that you can't pass your way through, you will end up with a whole bunch of promising looking moves being stopped after 3-4 passes.
All that said, I did quite well with the tactic. There were times that it frustrated me, but winning is winning.