Wouldn't shoot. Better to keep quiet and pass by without incident than tempt an uncertain outcome. Besides, I'm trying to avoid other players till I can locate a safe zone or friendly group of some kind.
Registered to say I agree entirely with Op's post and (buggy deaths aside) I'm very impressed by Day Z so far. My only real concern would be the future implementation of the humanity mechanic, but based on current evidence I'm confident Rocket will come up with something appropriately awesome.