Does it work or have they changed the pull ratio funny business?

Anyone?

It does work!There’s a thread on mtbr (can’t find it now) forum discussing it.
I know at least one person who has/is running a XT 11spd mech with a 10spd shifter and cassette.

^^ That would be me, worked a treat, shifted better on the expanded cassette than the 10s mech & RAD cage.

Also look at this thread from yesterday for a few others doing the same.

if you have a look here
http://blog.artscyclery.com/science-behind-the-magic/science-behind-the-magic-drivetrain-compatibility/

the derailleur ratio (sprocket pitch / cable pull) for 10spd shifters is (roughly) 1.2 whereas 11spd is 1.1. What that means is that the 11pd mech will move slightly less than a 10spd would.

It equates, when you calculate it through, to a movement from sprocket to sprocket of 3.68mm, compared to the standard for 10spd of 3.95mm, so it will slightly undershift by 0.27mm per shift. Over 9 gaps (10 sprockets) the total undershift is 2.4mm.

This isn’t usually an issue in reality. In fact, in my experience mechs often overshift slightly so the undershifting may actually improve matters.

Works fine for me using sunrace 11-42 cassette.

Can’t make out that art cyclery roady nonsense.