I ride the GNU B-pro now and the Burton Camber Twin.
If you are riding 3/4 per week blue runs plus jumping, then I do not think you need a beginner board.
I actually like the GNU B-pro a lot, but I like stiffer boards that can handle speed. The camber/rocker/camber combo plus the magne-traction makes it very good for me. It handles well on powder, ice, packed pow, slush, good for jumps and trees.
Not as good as the camber when pumping in/out of the pipe. Though I am just starting to try small boxes/rails, I do not think the GNU B-pro is good for boxes/rails and not as good as camber for pipe.
As far as the board size, 151 might be somewhat big, but it is just my opinion. Maybe try 150 or 149?
Can you demo boards? I would suggest to demo board sizes if you can before you buy to see what works best.