Ok, even though I have not been climbing on the MCRS for very long, I can honestly say that it is the best tree working saddle I have ever used!
It has some things that take getting used to, like the floppy side rings in place of the more normal forward set D rings. I flipped the knots on mine so instead of pointing upwards and falling back, they now face down and fall forward. That keeps them more accessible for me.
But beyond the need to adjust to the difference in some of the components and fitting requirements, this saddle rocks! Two things that stand out are the waist belt and the smoothness of lateral movement. The waist belt not only gives great support, in part due to its large size, but the inside being leather means it stays where you put it. In my opinion, nothing does this better than leather. The lateral movement is so smooth without being overly sensitive You do not have that side flopping feel you might expect. It feels perfectly neutral and non-restricting.
Anyone in the market for a new saddle should give serious consideration to the MCRS.