I love my penis, and I'm happily writing with them. With that being said, I'm learning what I like. The toughest part is that there does not appear to be anything approaching standardization-- I currently have three pens that supposedly had medium nibs, but they write three completely different types of lines, from quite broad to quite narrow. There is also whether the pen writes wet or dry-- how much ink is fed to the nib. I think I prefer a wetter pen, and a somewhat heavier line. I'm glad I didn't buy pricier pens, as I really needed to learn what I liked best.
You don't have to spend a lot to get a good pen-- my Pilot is the most expensive of my little menagerie, and cost $16.00. The Skilcraft that Jon recommended is my favorite writer, and cost under $10. On the other hand, the cheap Jinhao pen I got looks beautiful, but is a fussy writer, and not that satisfying. I might put a new nib in it, as it's so cheap, that it's still a good deal with a new nib.