I am cautiously optimistic (and at times, even more so).
I think the offense and the back part of the rotation are still very much question marks. That doesn't mean they won't pan out, but this is way too small of a sample size to say that Victorino and Napoli are going to pan out and that Igelsias is a big league hitter. Similarly, there are still question marks about Lackey and Doubrount and even Dempster to some extent.
Still, I think there's a lot to be excited about. Lester and Buccholz after strong springs and two outstanding starts seem to have regained their form. The defense should be stellar. And as others have said, the bullpen should be lights out. The minors also offer hope, as guys like Webster and Boegarts could be ready this year (stretch on Xander, but if Lackey falters, Webster could end up being the #5 guy--he had a stellar spring).
And as others have said, the attitude itself helps so much. Even if they were to miss the playoffs this year, it's still a much better environment to be bringing up these prospects in from the cesspool that was the Bobby Valentin era.