The lady and I decided to sample Dutch Boy Burger on Sunday night, which proved to be a rewarding experience. There's a far better write-up from New York Magazine here, but three points are worth repeating: the ingredients are high-quality and locally-sourced (the menu goes as far as to thank the butchers and bakers on the back page), the food is tasty, and the atmosphere, though currently truncated by the ongoing building-code drama, is lovely. I went for the Dutch Boy Burger (what else could I have ordered, really?), just under a half-pound of beef smothered in onions, mushrooms, and cheese that satisfied my craving nicely. The lady had the mac and cheese, which was a little on the small side for $6, but very tasty. The side of fries was particularly good, straddling the exterior/interior crispy/mushy divide well with the lightest hint of seasoning. Other reviews, including support for the veggie burger, are popping up on Brooklynian, and several people I spoke to raved about the feta-stuffed lamb burger.
We ordered out because we wanted to eat in the beer garden around the corner, but as soon as the code/permit issues are resolved, you'll be able to order directly from the staff at the bar and in the garden, and the kitchen will be open until 1 AM (no small victory for those in need of late-night bites in Crown Heights). There isn't room for more than a few tables in the little storefront, but the retro decor (including the sign!) is perfect, just right for sharing a milkshake.
In short, Dutch Boy is a most welcome addition to the avenue, though you didn't need me to tell you that. Swing by sometime soon if you haven't already.