He helped Petraeus write the counterinsurgency manual, which rocks; he believes in decentralizing battlefield decision-making, which is counterintuitive in a heavily wired age; and he believes that "the single primary deficiency among senior U.S. officers today is the lack of opportunity for reflective thought,"
All these things make us very happy, and fill us with as much hope as we can muster for Afghanistan. On the other hand, there are a few things worth remembering, including a nasty quotation that seems to reveal a lack of respect for his opponents, despite their considerable success against us. That's just foolish.
By the way, read the Danger Room post, linked above, and some of the comments. The first few say a lot, not only about Mattis but about the attitudes in play these days.