I used to know where I stood when it came to Shimano 9/10-speed rear mech compatibility between road and mountain bikes (or at least I thought I did), but I'm not so sure with the latest incarnations.
I want to use a 9-speed road cassette on my DH bike and I need to get a compatible rear mech. I know that the actuation ration has changed for XTR 10-speed (lower ranges too?) but has the same thing happened with road mechs? For example, could I use an Ultegra 6700 rear mech, or do I need to hunt around for an older model?