Voldur: Half-elf, half-orc (3.5) If you read it, you'll want to play it. Promise.

[Lord_Gareth]

It would learn tons of crazy skills with said weapon. And taking 10 levels to master one weapon (10 level PrC, presumably) with the level 5 minimum entry is still 15 levels...don't see how that's any better then 20...

Because, again, a PrC is supposed to take something that is broad and turn it into something narrow (also, any weapon mastering PrC should be five levels MAX). A base class is supposed to be able to carry a larger number of concepts than just one - a PrC does not have to. Cavalier, for example, is a Mounted Fighter. That's all it is. It's a narrowing of the Fighter concept to only involve Being On a Mount. A twenty-level "Weapon Master" class is a really narrow concept, whereas the /idea/ behind Fighter (realized with Warblade) is "master of warfare/combat", which entails much more. "Weapon Master" refines that to a narrower point.