HIGHLY underrated! A good example of how a major development delay can harm the general opinion of a game
Dark sector is an amazing 3rd Person "sticky" shooter (using stick-to-cover mechanics) with light survival horror zombie/infected elements. As has been stated many times already, Dark Sector is reminiscent of both Resident Evil and Gears of War. I was expecting more of a 3rd person action game like Devil May Cry and it took a little while to get used to the stiffer controls but once I realized that it was a mechanical clone of Gears of War, I really started to enjoy the game more. The graphics are top notch and are at least on par with Gears minus some frame rate issues, etc. The character designs are excellent with lots of great detail and the details on the walking tanks are sure to please any old-school Ghost in the Shell fan (or other Masamune Shirow works.) The soundtrack is excellent and atmospheric sound effects do an excellent job of making for a dark and creepy environment where applicable (especially the sound of taunt wires during intense mutant attacks!)
The original mechanics of the game are done very well and are very enjoyable and add to the already great mechanics inspired by GoW. The story may be a little light on narrative but there are certainly many less original plot lines out there so I don't understand all the complaints about the story. The voice acting is average to above average and never crosses the line into ridiculous so no complaints there either. One complaint of mine is the game manual. It is very minimalistic and repeated in English, Spanish, and French (which may not bother some people as they throw away the manual anyway) but it makes the game feel a little cheaper without a decent manual to help present the game.
After reading the reviews I was not interested in this game but after downloading and playing the demo on XboxLive I went out and purchased it the next day and have been very happy since. If you read the Gamespot review you will see that the only major complaint is with the weak story. I'm a fan of a good compelling story in a game but Dark Sector doesn't have a bad story, it just has a story that doesn't interrupt gameplay as often as some games do (one could make the argument that the developers were going for a minimalist approach to storytelling.) I really don't think it deserved to be downgraded so much just for this. Give it a chance!