Gary R.wrote a review of Mercury Wheels M1 Disc Brake Wheelset - Clincher on September 27, 2017
Familiarity: I've put it through the wringer
UPDATE: After riding these for over a year now, I can say I'm disappointed and would not buy again. Although they hold air when setup tubeless, there is a constant leaking of sealant at various spots around the rim. They just don't fully seal - even with TL tires. I've also broken two spokes on the rear wheel. Would not recommend.
First off, the sale price on these is unbeatable. For under $400, I can't imagine finding a better set of wheels. Roll nicely, well-built, look great, quality hubs. My only issue is with the tubeless setup. They were challenging to setup tubeless in the first place, and have continued to be disappointing as far as holding air and being burp-free. I have sealant stain on my sidewalls after every ride, regardless of PSI.
That being said, I'd still buy these wheels for the sale price and just deal with the tubeless challenges.
FWIW, I'm running Panaracer GravelKing SK 35s. On my previous Stan's rims I had no burping or leaking.