As if they weren't of questionable value, when I actually set up to use one, often as it appears it suicides my character. I guess like a vehicle spawning on top of you, except it's your own turret. Would be nice if it just moved us back if we happened to've moved slightly forward after placing it, after all they're not exactly easy to place and sometimes you're trying to do it quickly.
Put it out, when it's blue and 'deploying' you can run a mile away and it'll still get set up. Especially under fire, drop the turret, take cover, then go back to it.
I've never suicided, but while in a MAX my 'Guardian Angel Engineer' dropped a turret while meaning to drop the ammo box and it insta-killed me. That was a bit annoying.
What recently pissed me off is that some engi tossed out his turret right in front of vehicle spawn pad, tank that spawned before me got stuck on it, then when my tank spawned we both blew up. Before playing engi ppl should take IQ test or smth, if the result is too low - sorry, go heavy assault.