Huh the rival system is interesting.
Yeah I liked that, I'm not sure how it decides who your rival is?
Well just finished on Normal. I didn't fail any missions but had two missions where the countdown timer started on me, mostly from dying, the cover mechanics aren't great for avoiding rockets and grenades. I only did one "extra" mission to lower the defcon on the imperialist side before doing the final mission. Took me about 2 hours (not sure if the clock ran while I was doing laundry..). Total score of around 63k and ranked 365th although I think if you just kept playing extra missions you could run up your score infinitely?
I actually had a lot of fun and am going to dive right in to another run on a higher difficulty to collect the rest of the weapons, formulas, and dossiers. I really only used the pistols and an automatic. I used the DEFCON, Endurance, and Security Camera formulas on every run about half way through.
It's short, but I did not have a problem at all like a lot of the reviewers did with entering rooms in really bad situations. Sure there might be a guard standing right there but it was relatively easy to take them down in 2D with a silencer before they alarmed anyone. I saw it as part of the game. I did have one situation where I caused to much noise and someone on the other side of a room that I couldn't get to started raising the DEFCON level. It went through three levels before I got him, but again fair enough since I was making a racket.
Solid 7.5/10 game for me, might lower to 7/10 if more play-throughs get too repetitive since the first only took 2 hours.
Edit: Couple funny things. One officer blew himself up trying to kill me before I could get him to surrender and the game through up a hint box to not kill officers. Two there is no UK on their world map? What gives...