I'm bringing this thread back from the dead now that I've had the Mastery on my Mustang for a little while. My verdict is that the hype is well deserved, the Mastery is awesome!
It definitely cut down on some buzzing, and there was a noticeable increase in sustain. The narrower string spacing is also great, as my high e was too close to the edge of the fretboard for my liking before. Even though the stock Mustang bridge was supposedly the same 7.25 radius as the fretboard, the high and low e strings never felt quite the right height compared to the other strings before, but that was easily fixed with the Mastery. The intonation was also 95% there right out of the box, a couple of quick tweaks and it was spot on.
Yeah, it sure isn't cheap, but I'm glad I went for it. I highly recommend the Mastery to anyone with a Mustang/JM/Jag etc. that's considering going for it.
And of course I have to post a photo of it:
