I have one issue when it comes to airsoft as a training tool. The "honor system" works great for recreational games, but doesn't provide much feedback on the all too critical shot placement.
If your live target is wearing a t-shirt and the distances are realistic, then there should be no question where your "rounds" hit. Having been personally hit many times I can attest that AirSoft BBs do, indeed, hurt, and they raise a welt.
There is so much more to gain from AirSoft training than merely seeing if you can hit a live target. A good, reality-based AirSoft training program will fire you up emotionally and both activate and innoculate your sympathetic nervous system. It requires training to a specific objective, good role players, a good exercise controller and tightly scripted scenarios.
Attempting impromptu skirmishes may do more harm than good.