Fritzing is not a practical PCB CAD compared to Eagle or any other PCB CAD program, the part library is only the tiniest problem to solve. I would feel more comfortable sketching a PCB layout with a permanent marker than using Fritzing at this point.
It's open source and shows promise, but that doesn't necessarily mean it's any good yet. By all means put in the 10,000 man-hours of software development necessary to make it an acceptable alternative to gEDA, Kicad, or Eagle, I will root for you.