I have to say, I'm really happy for Mets fans right now. This is an incredible start. I'm generally indifferent to them and don't follow news about them, but was anything like this expected coming into this season?
I mean, the 2015 Mets went to the World Series, the 2016 team won 87 games. Mets have kept on promoting young, talented pitchers since 2015, and now that they are all healthy, their rotation looks strong and they have the depth to put a couple of talented guys in the bullpen, making the pitching a strength through all five starters and deep into their bullpen.
The lineup is fairly old with a lot of injury question-marks - counting on Cespedes, Bruce, Cabrera, Frazier, and Adrian Gonzalez to stay healthy and productive for a full season seems like a terrible idea, but as long as they stay relatively healthy, the Mets have a decent amount of capable fill-in pieces.
This start/this pace is obviously not sustainable/predicted, but with the talent and depth of the pitching, a healthy Mets team should be battling for the top of the NL East. On the other hand, injuries piling up with this roster would not be a surprise at all.