This is not Rainbow Six - just another random FPS game. Where's the original Red Storm?
Since when do you get hundreds of highly skilled, professionally trained, armed to the teeth with best modern weaponry terrorists? Wave after wave after wave of paramilitary specops with 50-kilo, 3-inches thick shields, all carrying 10000's of dollars worth of equipment you can't get from the Russians. Terrorists are usually happy if they get a semi-working AK from the 80's, these guys seam to have nightvision goggles? OK, for the sake of the game (remember - this is supposed to be a Rainbow game), lets say that this is homegrown terrorism, a bunch of soldiers going dark, organized under an ex-Rainbow operative (how silly is that - the story makes no sense).
This does not solve the linear, script-based flow of the game with checkpoints and no ability to save. Towards the end it gets boring and tiring - there are no tactics and the only thing expected from you is to shoot through hundreds of men. This detours from the original Rainbow series completely - you might've named this game "ZERO" instead of spoiling the series' name like that. Bottom line is: the game is totally unreal and goes against the high standards set by its predecessors, failing to deliver (hard task, no doubt, to go against your own principles).
The only thing "tactical" about it is using your other two team-mates - you can order them around, bash doors from the other side, throw grenades, flush out targets, they can support with covering fire and reverse. However, unlike in the older games, they FAIL (love that word) to act on their own, so basically you are stuck with two retards who have to be navigated and can't be split apart (who knows, maybe there's some love going on between the two), which hinders your tactical abilities significantly. The snake scope can be used to see what's behind the doors, you can tell your men which men have to go down first, which isn't really all that useful in my experience. Thermal goggles are useful in smoky situations. Love that gadget - feel like a predator.
The wide variety of weapons is sweet but you have to earn points to unlock many of them - a completely idiotic idea since the arsenal should be opened - it's mission critical to succeed after all, otherwise if someone dies you can blame that boy over there who didn't give me the gun I wanted. It takes ages to unlock the various weapons (half the time you unlock new camos and useless stuff like glasses and hats which don't change stats - just make you look cool). The armor is divided into sections and you can play around with the outfits for either more mobility or for more damage resistance. The little medals and ribbons you get are useless and makes me scratch my head why would anyone even bother programming these things into a game which is arcade anyway. I guess all these things are for the very demanding kids nowadays.
The game is very choppy/buggy/glitchy - even with my high-end machine the FPS drop significantly at times, with no real reason. The graphics are great but the troops move in a robotic way - the environment's FPS don't drop but the models' FPS do - a sign of bad development/programming - I'm still not sure if it's a port or not since the way the game behaves and talks to you looks like it was meant for a console - a shame really, could've been so much better.
If not for the multiplayer I'd give this game a 6, bus as in all games - playing with a friend or another human being just adds that 10% the games lack in single player.
It used to be that patience was rewarded - it seams to be the other way around in the 21st century.