It seems to me that you are on target.
That's Old Fuff in a nutshell.
Let me chime in late on this subject. First of all, I'm a member of MPIF and have been involved in MIM since the early 1980's. I'm also a longtime member of PMA (Precision Metalforming Association), and AMT (Association for Manufacturing Technology).
Like others have said here before, when done right, MIM is a perfectly acceptable technology for many applications. Unfortunately, an 1911 extractor is definitely not one of those applications.
MIM is sort of an offshoot of powdered metal (PM) technology. Some people erroneously call powdered metal "sintered" metal. Sintering a step in the PM process.
To make powdered metal parts, a metal powder mixed with a dry binder is compressed under very high pressure - we're talking 10's or 100's of tons of force. The resulting part -called a "green" part at that point, looks like a finished part but it only stays together because of the binder. You can take a green powdered metal part and crush it underfoot back into powder. The green parts are handled carefully and placed into a sintering furnace. During sintering, the binder is "cooked" out and the powder fuses togther to form the finished part. The part is almost (96% or so) as dense as a cast, forged, or machined part. There may be other secondary processes (like forging or machining) done to the part. PM parts can be made very strong - connecting rods for high performance engines are made this way. Not all parts can be made using PM however. The part profile has to be such that it can be pressed into, and pop out of, a mold along one axis. PM molds (called cavities) don't open side-to-side, they open up and down. For example, you can make a gear out of PM, but you can't make a firearm frame.
MIM is like a cross between plastic injection molding and PM. With MIM, a press that is very similar to a plastic injection molding press is used (A PM press is more like a metal stamping press). Metal, along with a heated binder that liquifies is injected into a mold. The resulting part is then sintered. MIM parts are not as dense as PM parts because they are not formed under nearly as high a pressure. MIM parts can be made with more complex profiles that would be impossible with PM. MIM parts are not as strong.
Both processes can be extremely cost effective - they both produce near net-shape parts without costly machining. However neither process should be used to make parts that have to be springy. These processes are more similar to casting than they are machining or forging.
Sorry to go on so long. If somebody wants, we can start a thread on investment casting, forging, and my favorite - STAMPING.