SpaceCowboy,
MIM is Metal Injection Molding. This process of producing small parts is analagous to solid wood compared to particle board. Instead of machining small parts from solid pieces of steel, Kimber finds they can save a few bucks by mixing metal fragments and an adhesive compund under pressure to form what looks like a solid metal part, but it's actually "soft" inside because of the method of construction. Colt, Kimber, and SA all use some MIM parts, but Kimber uses more than the others. The MIM parts aren't as durable as machined parts, especially slide stops, sears, and safeties which are all key components and may need to take some abuse.
I love many of Kimbers designs and their guns feel nice and have great trigger pulls, but until they eliminate the MIM components I won't buy one. I think the older Series 1 pistols are made with more attention to quality....but I'm no expert on Kimbers.