Well as an avid Uncharted player I would love for your input on this topic... I like it because I am not running around for ammo hopelessly anymore... i don't like it because if i kill somebody with a partner thn while I could inflict damage on them I'm takingthe 1 to 1 1/2 seconds to auto pick up ammo...
There's the ammo issue which you don't collect as much as you want anymore, there's the loss of strategy/ tactics as you no longer need to think if it's a good idea to get ammo while being shot at.
Oh and one thing that really pissed me off. I had a modified G-mal with increased ammo and accuracy, there is a G-mal on the ground with a laser sight mod only. I accidentally picked up that G-mal from the ground and I automatically collected my G-Mal with increase clip and accuracy for loving ammo.
In Co-op I had a M32 hammer, I accidentally picked up an AK-47 because I was trying to get the treasure. My teammate who happened to have another M32 hammer loving walks over to my Hammer by accident.