I think the quality of the Metal Injection Molded parts that gun manufacturers use have gotten better but Kimber had an issues with some of them years back. Springfield uses MIM parts as well (my favorite) but I had John Harrison in Kennesaw so some work on mine years ago. He replaced the crucial parts like the Firing Pin Stop, Slide Stop, Extractor. Can't remember what else. He also cleaned up the ramp and did a basic tune up on it. Cost was about $180. He is one of the best 1911 smiths in the country. Back then, he wouldn't do work on Kimbers though.
It's cheap to replace those parts with machined parts and easy/fun to do. I'm not sure it's a big worry unless you're putting 5000 rounds a month through it.
MIM parts on most 1911's unless you buy an Ed Brown, Wilson Combat, Caspian, Dan Wesson, Les Baer, etc. I would think that the guns coming out of Kimber's Custom shop have mainly machined parts.
Hammer, sear, extractor, firing pin stop, grip safety, thumb saftey, slide stop, plunger tube, mag release, ejector.