PT, as JEBar says, MIM has been around long enough now to be a legit way to make gun parts. In fact, you'd now be hard pressed to find standard production guns that didn't have some MIM parts. The exceptions tend to older, long-established guns that have been in production for many, many years (Browning SA-22) or some semi-custom or custom guns where customers specifically don't want MIM parts and are willing to pay the price to insure the gun has no MIM parts.
When MIM parts started to become common in production guns, about ten years back, it started a wave of protests with some gun owners, but the storm has pretty much died down, now that MIM parts have proven themselves to be worthy. For some, though, it remains controversial. Be warned.
The advantage of MIM parts is that they can be made to tighter tolerances that standard cast or tooled parts. This in turn, reduces the amount of fitting required, which, in turn, reduces labor costs. MIM also tends to give us more consistency in the fit of our guns. I've especially noticed improvements in the triggers on the same model of guns when the manufacturer switched to MIM parts in the trigger. Triggers on these guns have become more consistent, gun to gun, when the manufacturer went to MIM parts.
Some gunsmiths are not fond of MIM because a MIM part cannot be safely filed down. MIM parts consist of a hard outer shell and a softer inner core. Once that hard outer shell on a MIM part gets too thin, the chance of breakage greatly increases. MIM parts can be stoned, but we kitchen table gunsmiths should not grab a file and work a MIM part.