i have the ranch 5.56 model that took the rotary magazines, not the newer one with AR mag compatilibity. my model is smooth as butter and very accurate. it groups all sorts of ammo very consistently. mine loves 69gr OTM's, rounds usually touching at 100 yards.
the rotary mags are great but overpriced. i am also interested in the AR mag model although hopefully ruger gets this better than the mossberg MVP. i briefly had one of those but it jsut didn't run smoothly on AR mags. the issue with AR mags is since they only lock on one spot on side of mag, they really need a solid 4 sided mag well to hold in position (e.g. an AR). so if ruger gets the mag well nice and solid it should be functional. but if willing to drop some cash on the rotary mag ranch 5.56, i can say with certainty it's a fantastic rifle.