I've built a few pistol and rifle kits. Only production gun kits so far, but a semi-custom is in the near future. The kits I've built have been from CVA, Traditions, Lyman and Investarms. I've enjoyed building them, but realistically, you don't save any money building a kit usually. I build them for the fun of it, and to personalize the gun the way I want it.
That said, I have not had any good experiences with the CVA kits. Traditions kits have been simple and the parts fit pretty well. Lyman and Investarms are top notch kits. I haven't built a Pedersoli kit, but I am looking forward to trying one. I like their guns.
Generally for most kits I've built, the parts fit relatively well but often still need some hand fitting. Inlets need adjusted, screw holes often need filled and redrilled to be in the proper position, metal parts need filed and fitted, etc. There's always a lot of final contouring to do to the wood. I have yet to find a kit that was just sand, stain and finish the wood, and blue or brown the metal.