Difficult, and with room for improvement.
I stopped playing after the first few stages. I have many requests in terms of improving gameplay. The idea was fine, classic bird's eye shooter. Not exactly sure about story/plot, but the idea and genre of the game was a good choice. Here's, well, a potential list of improvements.
-Make weapon switching faster so you don't have to wait a few seconds in the middle of combat.
-Bullet time was a good idea, but I think it should go up after killing an enemy or finding a bed to rest it or something. If it recharges over time, it's too easy to just stop playing for a little while until the bar is full.
-Don't start the game with every type of weapon unlocked, with ready to use ammunition. Make the players earn the upgrades.
-Make upgrades for speed so you can move faster.
-Don't give the bullets such a wide scope of damage. I was being shot at, and the bullets were hitting the wall behind me about a foot away, but it still counted as being hit.
-Few lag issues, particularly when you get shot and the blood effects kick in. After that you can't shoot back because your computer slows down too much.
-Have upgrades in stage. Like I said, perhaps a speed upgrade, or first aid kit, or kevlar vest. That would be good.
-Have snipers and things- military tactics.
-Give the protagonist a story. Not just a "soldier" who's killing a whole heap of other soldiers. Where's the patriotism in that? =p
-Perhaps a cone of vision, ie line of sight, would have also been a good upgrade, so you can stay hidden from enemies and try and sneak past them.
I also noticed that once you initiated bullet time, and then took it off, the bullets traveled at bullet-time speed. The bullet time itself was a great idea though! Great idea! You just need to work on how it's used a little more.
Well, that's all I have to say. Characters were a little slow and all, but I think this game could really go somewhere if you considered some of the points I mentioned. Fair game though, 7/10.
~VelvetDarkRocks~