I currently have over 2,000 miles on a set of MSO 700x40 TR, and I am very pleased with their performance - as in NO PUNCTURES!! I run them tubeless on a set of HED Belgium. I ran them in the Almanzo 100, DK 200, Heck of the North and lots and lots of gravel training miles (note I have a 2nd wheelset with 700x30 road tires for non-gravel riding). I have no idea how they perform speed-wise compared to other tires, but they seem fast enough for me. And the fact that they havent flated in a race makes them faster than having to stop and fix a flat.
I will definitely be putting a new pair of Donnellys on my bike for 2019 - most likely another set of MSOs.
Got the MSO 40s in 700c, tubeless. Mounting was not overly difficult. One of my pair inflated directly from a floor pump, the other required the compressor. Sealed (orange) fine. So mounting experience was very good (DT Swiss aluminum hoops). Rode a couple fondos (and other rides) and they took the abuse well. The Fondo was especially abusive with lots of sharp basalt rock and steep climbs. I picked these specifically because of the anticipated conditions for the Fondo and I am impressed. They have pretty good traction as well and the center bar rolls pretty well on the pavement.
Used these tires (700x50c) on my Specialized Elite gravel bike and rode the the first phase of the Great Divide Ride from Banff, AB to Whitefish, Montana. Had about 45 lbs. of gear on bike (self supported). While I could have used a wider tire to handle the fast descents, these tires nevertheless performed exceptionally well. Never had a flat either-)
Without the gear on the bike I could have ridden almost as fast as on my mountain bike. Recommend these tires!!
Ran them tubeless with 35 psi at this year's Lost & Found gravel grinder. They provided reliable handling in the rough stuff, and were smooth on the pavement sections. No problems through a bunch of rocky sections where others suffered flats. I was very pleased.