Ehh... I really don't like them. I like to be able to survive a shot, no matter where it lands, even if it means I can't get headshots myself.
I like how Team Fortress 2 handles it: only the Sniper's Rifle and Huntsman and the Spy's Ambassador can headshot, and, even then, it's only a guaranteed critical hit; if the rifle or bow aren't charged enough, even a headshot won't kill everything in one shot. Bodyshots are also very effective with the rifle because a fully-charged shot will do 150 damage, which means it will kill a Scout, an Eyelander Demoman with no heads collected, a Medic, Sniper and Spy in one shot, no matter where it hits, assuming they're not over-healed.