I personally think Fritzing has the potential to become something much larger than what it is. From what I understand, it will output standard Gerber files, so in theory if the board maker will accept that format, it should work.
With that said, I have decided that when I get around to doing a real PCB and learning this stuff, I do not plan on using Fritzing. I also don't plan on using Eagle, simply because I don't want to be limited by size or board layers (and I can't afford the more expensive versions; plus I want to do commercial stuff).
Instead - I plan on using and learning the gEDA suite of tools and/or kicad (and others). While I know the learning curve is anything but shallow (from what I have played with - admittedly only gschem - and from what I have seen online - gEDA's learning curve makes Eagle's look "easy"), I feel that ultimately it will be worth the struggle.
