Comment by cortesoft
My annoyance with story points is how it always seems to end up returning to “how many hours of work will it take”, even though the whole point of using story points is to get away from trying to predict how many hours of work something is.
You don't predict that. You measure it.
That is, we estimate a certain set of tasks. For this two-week sprint, we're going to try to do a subset, and that subset adds up to 20 story points. After two weeks, how much did we actually get done? 7 story points. Next sprint we did better, we got 11 done. After a few months, we settle down to an average of 10 story points per two week sprint. Now we know how many hours something is (estimated to be) based on the story points.
Note well: This velocity is a function of the team. If the team composition changes, previously measurements of velocities are no longer valid.