Matt Tolbert's off to a good start, but really, that's all that it is: a start. Before the season, the following projections were made for Tolbert:
.256/.317/.358 -- PECOTA
.256/.308/.370 -- CHONE
.256/.306/.366 -- ZiPS
Which is really a remarkable amount of agreement for three completely different projection systems. Thus far, Tolbert has had 13 at-bats and 15 plate appearances. Given his projections, we would expect him to have 3-4 hits, been on base 4-5 times, and have 4-5 total bases. So far, he has 6 hits, has been on base 8 times, and has 7 total bases. That basically represents an improvement of three singles and a walk over what we expected.
Three singles and a walk aren't going to convince me of anything. And it certainly doesn't strike me as compelling evidence that Tolbert has been an incredibly overlooked prospect and we were totally underrating him all this time.
However, I've been overlooking him from the standpoint that the rest of our options at second base are so underwhelming. Punto and Harris are both flawed players, one with an awful glove and one with an awful bat. For this year, anyway, Tolbert probably can't hit as well as Harris and he probably can't field as well as Punto. But, he can also probably hit better than Punto and field better than Harris. Overall value being roughly equal, I generally prefer starting position players to have their value balanced across hitting and defense rather than have a big flaw in their game.
Casilla has certainly been unimpressive in the majors thus far, and there is some minor league defensive data out there that shows him as a below average defender at 2B and SS. Plouffe is supposed to have a pretty good glove, but it seems unlikely that he has a much above average glove, and he doesn't project to be a better hitter than Tolbert over the long haul. Our middle infield of the future could well be Plouffe-Tolbert, though Casilla isn't be far behind. If things go well for those guys, they could be contributors in the way that Jason Bartlett was a contributor to the 2006 team--fairly solid players whose youth gives you the financial flexibility to spend money elsewhere on the team.
So I'm a little higher on Tolbert's future today than I was a month ago, but mainly because I've actually stopped to consider that he might be a contributor. His early season success makes his rate stats look nice, but doesn't do anything to change our long-term outlook on his value.

Are you saying all this in spite of the fact that he put up solid numbers throughout spring training? And that he's hit the ball hard since then?
Spring training is like two weeks worth of regular season statistics, if that. Remember Bo Hart?
Oh man I loved Bo Hart! When was that, like 2004? 2003? He was Nick Punto before Nick Punto was Nick Punto. He was always on Sportscenter hustling around on his little legs and making some ridiculously unnecessary slide on another clutch hit. To me, he was the baseball version of Rudy.
Shortly after that I discovered baseball blogs, which promptly slapped the sentimental-love-for-the-scrappy-little-guy right out of me. I can hate the Nick Puntos and David Ecksteins and Darin Erstads with the best of them now, but I will always have room in my hart for Bo. (see what I did there?)
clever, NG. You're like, an English major or summat.
hey, everyone needs a life-mascot. You can eat your Hart out.
me, I'm sticking with Cesar Tovar.
Tovar is a good choice. He was a real piranha; he had serious teeth.
Also, just yesterday, someone else commented that Tolbert might lead the league in hits off fielders' gloves, which suggests to me he hasn't exactly been roping the ball into the gap with every swing.
Well, I'm giving Tollbooth credit for seeing enough pitches to actually draw a couple walks.
Heck, I'm glad Tolbert is doing well just for the sake of potentially knocking Nick Punto down a notch on the IF depth chart. And if Tolbert gets ahead of Punto on the depth chart - what point is there to having Punto on the team? I guess I don't expect Gardy to actually get this logic, but I'll hope a little bit.