I suspect there are MIM parts in most if not all my personal firearms. The only part I’ve ever had fail was a plastic trigger on a Sig Sauer P938. Even that didn’t fail to the point of total non-functioning, it just failed to the point of my standards.
Based on your comment, I looked up this 3 part discussion of MIM I found interesting. This is an execerpt from Part 3.:
“RevolverGuy’s sources advise that the MIM parts have maintained better tolerances than the old ones and are much stronger than the old ones, too. While they may not be as attractive to some customers, they’re a lot tougher, are improved in their design, and will offer better service life.”
You are right about that! I polished my Delta Elite and it shows body oils even if you just get close to it 
BTW, a wipe down with alcohol is the quickest way I’ve found to clean it back up.