Extremely good concept but it could use some polishing.
The game map itself is extremely large it covered my tabs screen and also, as SkyFire2008 put it, the ghosts could pass through walls which, even though I had great weapons in hand, can ambush me in the back and also in the front. The ghosts would sometimes cover chokepoints and trap me in a place where there's no space to run. Also the loading is horrendously long. I almost slept through the loading screen.
The music was great and the shooting mechanics could be a bit better. The graphics were great and has that way to make it look gorgeous while not lagging and shitting on my computer monitor. Make the ghosts more easier, take down the ability to pass through walls. Hopefully you make a sequel out of this. A great concept can't be completed without great and fair mechanics.