OK, having played it for a bit, and I loving it so far. Here are some things I think would improve the game:
-Like it has been said before, the main character needs some recovery time after being hit by an enemy. As it is now, physical attacks are useless, and as soon as enemies gang up on you you are pretty much dead, there's no way to get out.
-As it has been pointed out, being able to "see" a cone of vision, or the extend of the enemy sight would be awesome.
-When you die and respawn, the enemies that were looking for you should be gone. Sometimes I die near (or in) a respawn point only to be killed again by the same mob that killed me before.
-Mines are too cumbersome to use. The fight against the tank becomes needlesly complicated because of this, as you have to lift a hand to reach the mine usage key. Maybe you could have a "use item in x slot" mechanic? Just like you can equip different wepons and then hit fire, you could be able to equip a type of explosive then use it.
-Sometimes the game tries to be too modern for it's own good. Why do I have to press a key to pick up an item? I should be able to just walk over it to pick it up.
-The box doesn't seem to be doing much. Sometimes it just unequips by itself
-How come I can't use my cigarretes to detect laser beams?
-There should be a hotkey to get to the radio when called.
-Dogs don't show up in the radar.
-Is the jump any use?
-Why isn't the TNT just pastic explosive? It makes more sense, militarywise.
-It would be great to just type the passwords instead of using the mouse.
-Why can't I keep my rations equipped to avoid being killed that easily?
-Controller support would allow for different analog movement speeds
I hope these suggestions are useful for you