Honestly, I actually liked the singleplayer. It ain't outstanding, but it's worth it's 20$. And no, it is NOT the linear railroad he claims it is. It regularly is (and the early levels are just that), but not always. For example, the mission "Fallen Angels" is split in three parts. First is a combat. Linear, nothing special, but you can order two CLAWs to shoot targets. Second is a semi-stealth section as usual. BUT you can go and hide whereever you want! No, really. For example, in a dinner, I was told to wait at the entrance to hide. I ran through it and hid at the exit. Worked fine. Following that I ran to the next car instead behind a pillar as ordered. Again, it worked.
And following THAT is either a driving sequence with a linear track and two or three sidepaths every now and then - or a simple (yet rather unforgiving - miss one target and you lost - and bit boring, too) railshooter.
Also, the "semi-option Tower Defense" is actually a "FULLY OPTIONAL Realtime Strategy". Tower Defense is something ENTIRELY DIFFERENT, MY DEAR YATHZEE! (Espically considering that in three out of the five missions, you are the OFFENSE! Only ONCE you are the DEFENSE and once, you're escorting four trucks where at least one has to survive - not hard, but boring). Yes, the AI ate the soup with a fork, but at least you can count on them to shoot the target you ordered to shoot. And the fact that you can take over a guy and go nuts yourself gives it a nice change, allowing you to pull of things you couldn't do just as commander.
And yes, he left out 2/3 of the game (Multiplayer as usual and Zombie Mode), which no matter as what you see his videos (Review or whatever), it kind of makes it pointless in that regards when he didn't even bother to play more than half the game.
Note for the Stealth suit - it works, if you keep some distance and aren't shooting. The enemies see you the same way you see them. So, obviously they shoot you if you turn that thing on and then hold up a big, red arrow over your head saying "SHOOT HERE, PLEASE!"