Finecast is Citadel Miniatures' wonder material that is finer than metal and holds detail better, cooks your dinner and- no, wait, maybe not.
I have purchased resin miniatures before and been very impressed with them. Not so with Finecast.
Finecast is sort of a plastic/resin hybrid and (in the best cases) holds detail very well (like modern plastic minatures can). Its surface texture seems to take paint better than plastic, but it also seems to be quite grainy and often very pitted. In the worst cases (an Incubi boxed set I picked up recently) the molding seems not to have taken at all in some areas, leaving them rough and half-finished, with a tenacious pink goo on them. Bizarre.
I had really high hopes for Finecast, and when it works, it works well, but in the majority of my experience, it is an astoundingly poor product. I don't want this to be an attack on Games Workshop, but it is disappointing that one of the world's leading toy soldier companies has dropped the ball so badly.