I'm half for this. It's odd peppering a guy with a PPSH, then watching him sprint away. True, there is the whole "People have been on drugs/adrenaline/crystal meth/etc. etc!" but those cases are few and far between.
Especially considering we are dealing with a majority of large calibers. I couldn't imagine hitting someone with a .308 in the torso and they just shrug it off, unless I missed everything vital.
On the flip side I don't think all wounds to have lasting effects, even if they hit limbs. Maybe if it hits bone (is bone structure even modeled?), but not just muscle, and tissue, damage. We had gentlemen in Iraq take 7.62x39 to the thigh, pack the exit wound, bandage it up, and stay in the fight at full mobility without pain killers. Granted it took him WAY longer than it does in game, like a good 2 minutes. Did it hurt like all hell? I'm sure, but if your life depends on you not being a gimp your body will make some amazing things happen.
-Paas