Well I finished it. All in all its actually a really fun action title, but I definitely dont think its worth 60 clams, it would be worth it after a price drop. It's an all around well made game, and the glaive mechanics is really what makes it worth a look, however other than that, Dark Sector borrows from a lot of other big action titles that have been released. Practically almost everything in the game reminded me of one action title or another. The cover and fire gameplay and some of the environments feel like they are pulled right out of Gears of War, theres a black market merchant where you can make upgrades and purchase guns just like in RE4. You can perform finishing moves that are reminiscent of Assassin's Creed, and the mutated freaks you fight look very much like the flood in Halo. But not to say that any of this is bad, all these little borrowed gameplay mechanics do work well together and in the end you catch yourself getting giddy as you decapitate, electrocute, and set victims a flame with your bladed boomerang of doom.
But like I said, the glaive weapon is the only thing that really sets it apart well enough from the other big action games. There are various little puzzles you'll run into that require you to use elements of the environment to get by. Cooling off fires, opening doors by surging control panels with electrical currents, and setting things on fire to progress on. I kinda wish they took some things with the glaive a little farther, but the abilities you get freshen things up enough to get by.
The difficulty felt just right, there was no option to set it but they seemed to nail it on it as nothing is too easy or too hard. I did have a lot of trouble with one of the boss fights but its not that it was cheap, I just had a hard time figuring it out and it ended up being easier than I thought it to be. After you beat it, there is a brutal difficulty mode that is unlocked but I feel like I've gotten my satisfaction out of the game for now.
As for the story, yes, just like other reviews have mentioned, its rather poor. Nothing is really explained, you don't know who your really fighting or why but the cutscenes try to make themselves really dramatic like they are trying really hard to make you care, but it fails. A nice intro into the world giving a descriptive background would have worked, but all you really get out of it as that theres some alien disease, hell I dont know if its even alien, its just bad and your character gets it, but it makes you a killing machine which is awesome and thats all you really need to know. At least the cutscenes you do watch are pretty short.
In the end its like how I expected it to be, I had a lot of fun, but its rather short lived, and theres no real incentive to go back to it since theres nothing to go back to it for. There's no bonuses to collect or secret objectives, its all straightforward. The multiplayer I have no real interest in as they pit teams against each other where one player is uber strong for each team. I hate those types of games.
I recommend checking out gametrailer's review of it as I felt its pretty spot on to how I felt about it.