I say no.

They are hot, add weight, and only cover the upper body. Besides the already stated fact they are not "bullet proof" to all calibers/types of weapons, they are not knife proof.

To me, the worst part is they add a false sense of security. You may do something you wouldn't normally do if you are wearing one.

I've got a flak vest out in the garage. It protects some tools I guess. Never wear, but don't want to toss it.