This is anecdotal as well, but we recently test drove a number of 2015+ GM Suburban/Yukon/Escalades, and the two with Magneride dampers had a noticeable shake/rough ride from 75-80.
2015 Suburban LT Z71 stock 18" wheels - Z71 package made it ride a bit stiffer, but no issues at speed.
2016 Suburban LTZ stock 20" wheels - Magneride, Had the unpleasant ride 75-80 MPH.
2016 Cadillac Escalade ESV stock 22" wheels - Magneride, Had the unpleasant ride 75-80 MPH.
2017 Yukon XL SLE stock 18" wheels - No issues with the ride, in fact this one rode the best overall of anything we drove.
2017 Suburban LT stock 22" wheels - No issues at any speed, although with the 22's you do feel more bumps (no surprise), but it is smooth at all speeds, no issues 75-80. We ended up buying this one.
After the first two experiences with the magneride equipped vehicles, I ruled out purchasing any of the GM triplets with those shocks, as I didn't want my first thing I do with a new vehicle to have to install sensor foolers and retrofit regular shocks onto it just to make the ride acceptable.