If one is religious about prepreping a barrel, and consistently shoots moly and is diligent in working up a load (not according to manuals), then I can see a lot of plus's with moly. I went down this road from 2000-2002. I just didn't like the hassle. Also if you clean out a barrel back down to bare metal again, erratic performance may happen, and in fact if you built up a load that is on the edge of a hotrod, you can get pressure signs shooting in a bare barrel again.. Also, I had erratic performance after shooting 100 rounds or so. Lastly, its slightly hydroscopic.

A few real advantages I can see is true varmit shooters that pop off a bunch of rounds with some real barrel burners. I have seen 22-250's AI's with over 4000 rounds that was loaded full tilt and no huge throat errosion. Where I have seen 22-250AI with 1000 without moly with significant throat errosion.