There's something about a fountain pen. I have a few, and without fail I write more neatly, and make fewer mistakes, than when using pencil or ball-point. I think it's that they demand slightly more concentration on mechanics to make them work, and that's enough to make a big difference in the writing quality.
Eh… I have one I use daily (a Pilot/Namiki retractable nib) and it certainly hasn't made my handwriting any better. It is nicer than a regular pen though.
That's simple. Dip and fountain pens allow you to create lines of different thickness, which can result in interesting calligraphy. It's simply impossible with ball pens which produce constant thickness lines.
