Stainless Steel Tumbling Media aka STM

I was interested to know if anyone uses this stuff found here?  $50 plus S&H I to get 5 lbs is an investment in media.  Based on what I can read it sure sounds like magic though.  All in the funny if not silly pursuit of clean brass.  Mostly I want to ensure the inside of my cases are clean and carbon free.  And, as of yet, I have yet to invest in any media or case cleaning system.

I was doing some research and found these before and after pictures and find it hard to imagine brass could get this clean on the inside.  I know, does it really matter and can it affect case volumes?

Before

And after

Or, go to this link and read a very long thread discussing the use of SS media.