Wasted potential
The environments, which at first look nice and dark and creepy, soon become uniformly drab and dull. The glaive is a cool weapon, but due to imprecise controls, never becomes a viable combat option. This is a problem because you'll frequently run out of ammo, which you can only replenish by finding it lying around the levels - you can't even buy ammo at the store where you buy weapons, which struck me as completely bizarre.
There are only 2 kinds of enemies - soldiers and zombies - and 2 kinds of bosses - big robots or big zombie monsters. The game occasionally tries to shake things up by throwing the odd puzzle in your way. Unfortunately these puzzles are at once uninspired and frustrating, because the environments are so drab it's often hard to pick out what can and cannot be manipulated.
Added to this is the fact that tutorials are sparse and inconsistent, so you'll often go through a lot of trial and error (meaning you'll die frequently), which is annoying because the game employs an autosave system and no manual saving, so if you die you have to restart at the beginning of an area, and all the enemies you've dealt with will be there again.
If you're dying to play this game I would suggest a rental, but to be honest there are so many games of this type out there, and the majority of them do everything much better than darkSector.