I feel like he was pretty hamstrung by Kenny for the first few years of his "GM" tenure, and the rebuild marks the time when he actually got to start doing what he wanted. In my view, Hahn's defining move is getting players to sign long-term deals early, which drastically raises their value. I'm happy with the young talent that he has acquired since the rebuild began. I was hoping the Sox would get Machado, but the fact of the matter is Moncada (in his breakout year) was pretty significantly better than Manny last year.
Last season would have been early in a rebuild to start adding veterans, I think. Now that several of the young players have shown that they are good (potentially great) major league players, and a couple more are right on the cusp, the Sox know what areas need to be addressed via free agency. Jerry's track record is very poor in regards to free agents, but the White Sox have literally never been in this position, financially, so I'm giving him this winter to change his stripes. They could add three absolutely premiere FAs, and still only put themselves near 11th or 12th in payroll (where they were from '05 until the start of the rebuild).
This is Hahn's one chance, though, in my eyes. This rebuild is his baby, I think. It's the first thing that doesn't feel like it has Kenny's fingerprints on it. I am very happy with the early returns on the added youth, but if the rebuild does not produce a multi-year playoff contender at some point, then Hahn has failed, and he must go. I think the "beginning of the end" of a GM's first attempt at a rebuild is a pretty slanted spot to judge him, statistically. But, of course, I am an optimist by nature.