they've recently added a tubeless version of these. seen here: http://www.cxmagazine.com/maxxis-mud-wrestler-tubeless-ready-cycloc...
They're good tires for all-around....not sure about actual mud though. The knobs seem a little small to me but the spacing seems really good.
I'm using the Mud Wrestler set up Tubeless on Stans Grails. No complaints with two races running low 20's and no burps. They seem like a good all around tire. Did the early morning race here in Chicago last weekend. Course was definitely muddy and these held lines and shed mud really well. Second race was hero dirt and railing corners was child's play.
Peter, are you using the tubeless version? thanks