The thing about A-Gon that has been impressive to me offensively is merely that he is consistently making contact. Frankly I couldn't care less about whether he hits .300 right now. He just needs to not look overwhelmed, occasionally move a runner over or get a pitcher to throw pitches, hit a sac fly or bunt if it comes down to it, etc.,. He simply needs to come through by doing the least amount possible to not completely be harmful to this team and he will be fine for them moving forward.
Defensively he seems to step up to make plays when he absolutely has to. I think the difference between he and Nick Green is significant defensively, as Gonzalez seems to make the more difficult and impactful plays if given a choice. Pedroia does the same thing.
We see a lot of Pedroia ranging toward 1B and still making the long throw back to get the lead runner--sometimes even the middle runner--at 2B. Aggressive defensive plays like this statistically increase the team's chances of winning and clearly give the pitcher more confidence while reducing the number of "stress pitches" with RISP.
For whatever reason, Gonzalez just plays more like a "professional" shortstop than a lot of other SS have with the Red Sox lately. To me, the shortstop needs to be the most self-assured and confident fielder in the infield. With Lowell, Pedroia and Youkilis on the infield already, that's a pretty tall order, but it is a reasonable expectation for a team with as many resources as the Sox. Gonzalez isn't that guy longterm, but he does play like that now.
Orlando Cabrera brought the same sense to the Sox defense in 2004 and it changed them considerably. The stats don't always back up the value of their plays, but the impact is immediately present.