In my experience, they have negative usefulness in general.
I did work at one company that used an Agile/Scrum process, and though we didn't estimate actual time, we did estimate effort to complete tasks. That worked pretty well: we had an idea which tasks would be easy and which would be hard, and used that in sprint planning to more effectively use developer time.
But the key is no one was held to an estimate, since it was only that: an estimate. If something took 2x as long as predicted, oh well: we just adjusted our planning and worked around it, delaying other tasks for instance.
The problem I see is when managers demand an estimate, and then turn the estimate into a deadline and try to hold developers to that estimate no matter what.
I did work at one company that used an Agile/Scrum process, and though we didn't estimate actual time, we did estimate effort to complete tasks. That worked pretty well: we had an idea which tasks would be easy and which would be hard, and used that in sprint planning to more effectively use developer time.
But the key is no one was held to an estimate, since it was only that: an estimate. If something took 2x as long as predicted, oh well: we just adjusted our planning and worked around it, delaying other tasks for instance.
The problem I see is when managers demand an estimate, and then turn the estimate into a deadline and try to hold developers to that estimate no matter what.