I bought BF:Bad Company last week and have played through the first three missions now. One thing I wonder though is if theres any reward for, or point in collecting gold bars on the levels besides for achievements. They story seems to be pretty focused on them, but so far I haven't found any use for them (or the collectable weapons for that matter).

So far as I know there isn't.  I don't remember there being any point to it other than achievements. I played through the game when it launched, didn't find all the gold bars, and didn't feel like I missed out on anything. I could be wrong through. Maybe I did miss something....

It's pretty silly to say "except for the achievements." 
 
What's the point of killing people? Except for not dying, but what's really the point?