There's "best use of his skill set" individually, in a vacuum. In that sense, full time closer is definitely not the best use for Alfredo Aceves.
But then there's "best use of his skill set" in the context of the team and the time period.
If Aceves is still the closer in June, then that will either mean that he's been much better than expected in the role, or that the rest of the bullpen has been much worse than expected.
For the moment, though, the team has 13 pitchers – and so, less of a need for his "3 innings today, 1 inning tomorrow" skills. Melancon and Padilla could be candidates for the closer job, but one had a shaky spring, and the other had a spring slowed by injury. Aceves is trusted from day one (and the circumstances of yesterday's game shouldn't shake that trust).
When the Sox settle in to a 12-man staff, and other pitchers (we hope) settle in to the season, I think we'll see different roles. But for now, Aceves closing does make some sense to me.
Check it out. An avatar.