Footnote: on the legalities
Just so we understand what's happened here, there are two sorts of presidential clemency: Commutation is shortening a prison sentence, while a pardon is thought of as a sort of official forgiveness for whatever the crime was.
An important difference is that commutation leaves the conviction and the assumption of guilt intact; it does not do away with civil disabilities such as not being able to sit on federal juries or, in many states, to vote. A full pardon, like commutation, doesn't suggest innocence, but it does strip away many of the effects of a conviction, allowing the person to vote, sit on juries, and possess firearms, among other examples.
So I wish Chelsea Manning had gotten a pardon rather than a commutation, but her release remains really good news.
If Obama had followed through and issued a pardon for our other American hero, Edward Snowden, that would have been fantastic news. But of course he didn't to what should have been no one's surprise.