More fountain pen reviews than you ever thought possible: http://www.youtube.com/user/sbrebrown
Entry-level fountain pens: http://www.youtube.com/watch?v=UId3hHz4bjk
The main issue with using a fountain pen I've found is that sometimes people will ask to borrow a pen, and now you have to vet them carefully to check that they don't hold the pen with their fist all scrunched up and the nib pointing straight down.
Unfortunately the basic market for high-quality new pens seems to be as a luxury accessory, with price inflation to match. There's an apparent increase in low-priced new fountain pens in the last few years, but they all seem to have extremely stiff nibs made of thick steel or something.
[I met a guy in Boston who had a small open-by-appointment shop with like 4-5000 old fountain pens, most of which were not really pretty enough to sell well as boutique/antique items, but many of which wrote very nicely. He bought a lot of pens and eeked out a living selling the prettier ones; I'm not really sure what the eventual fate of the rest is.]
† There are tons of super cheap and nice flexible nibs available for dip pens, though I guess many are not well suited to general writing.
I've seen nibs for dip pens in the local art-supplies shop, including drawing and map-making nibs, but it's just not practical so I haven't even tried them to see if they're what I want. If they were, I'm puzzled why they have to be dip-only, presumably a fountain nib works differently?
Having searched a little it seems 14K gold alloy is best, but modern rules mean it can't be labelled gold so isn't manufactured any more. http://www.richardspens.com/?page=ref/ttp/materials.htm
Most drawing / calligraphy nibs only work well when you're pulling the pen (e.g. try pushing with a pointed nib, and you'll quickly tear up the paper or break the nib). Because of this, they can be of fairly simple construction, made of flat uniformly thin metal (generally just steel AFAICT). As they're relatively cheap and easily replaceable, it's not a huge deal if a nib breaks, you just put in a new one, and you're not out too much money.
Fountain pens, on the other hand, have to work reasonably well when pushing the pen too, so you can't really make them entirely out of thin flexible metal. Together with a more complex ink delivery mechanism, the nibs seem inherently more expensive, and so tend to be part of the pen rather than a disposable part (I imagine the average person who just wants to write his stuff wouldn't be very happy if they had to constantly replace the nib either). By making them out of relatively stiff metal, you can sort of avoid some of the problems while still using cheapish construction. I don't know why gold is better offhand, but I imagine it may be better able to put up with the forces involved when the nib is thinner and more fleixble, without breaking.
Gold is good because it's flexible but pure gold is too soft and wears too easily so an alloy is used. 14K gold alloy seems to be the sweet spot between flexing and durability, modern 18K loses the former.
Edit: Noodler's website, http://noodlersink.com/
I happen to have a Parker Vector, but many people swear by the price/performance ratio of Pilot 78G. (I believe it's 78G, it's something-G anyway.) It's cheap, go ahead and try it. And keep in mind that Japanese nibs are finer than the designation (F, M...) would suggest.