Longboard Nose Concave
I'm of the opinion that if your noseriding talent is high, you'll be able to noseride most longboards regardless of nose width, rocker or bottom contour. I don't want to suggest with this comment that nose-concave is a crutch, but rather that a tool to 1) enhance your experience & 2) lend a little more levitation to those learning.
As I was growing up all my longboards had more "defined-edge" (taped-off), tear-drop nose concaves. A lot of that was based on some of the trends of the 90s. I've spent the last 8 years, however, switching over to blended concaves and/or just noses with a flat contour. I've gone to the blended concave for two reasons: firstly, it's quicker to shape. Secondly, my feeling is that one of the most influential features of the nose concave is the plane break at the back of the concave; the point where the concave ends and the rest of the bottom continues. If you have a deep side-to-side curve, you don't need the defined edge of the tear-drop style concave. The side-to-side curve (an increase in surface area) and the plane break are working in tandem to provide lift when you're on the nose.
Noseriding (regardless of concave) is an act of stalling in the curl, and I've had some interesting feedback from the various non-concaved boards I've had. Especially over the last few years. They give me the feeling that my noseriding is a little less a trick than it is a functional aspect of the waveriding; a transition between those moments of speeding up and slowing down. I really appreciate that (even though my noserides might be a little longer with a concave).
However, as a rule of thumb, I generally recommend a blended concave to my customers. It is part of my stock bottom contour and incurs no extra fee. If you love noseriding (as I do), want extra levitation or are taking your first cross-steps, then you'll appreciate the extra bit of lift.