Oniwrote a review of Shimano XTR SL-M9000 Trigger Shifters on December 29, 2015
Familiarity: I've used it once or twice and have initial impressions
Spent the past weekend swapping out the 10 speed XTR/XT drive train for the 11 speed XTR/XT drive train. I replaced an XTR cassette and shifter with an XT cassette and XTR shifter, an XT derailluer with an XT derailluer and a Wipperman chain with XTR.
Rode last night on the usual Monday ride which involves 45 minutes of grunting up a steep road climb followed by some nice DH back down.
I shifted it a lot, just trying to get a feel for it. And to try and not bark. Here's what I found: I think the XTR 10sp shifter is nicer, it has a better feel to me and it's more ergonomic. . 11sp feels plastic. I also can't get the shifter adjusted to fit my fingers. It seems like Shimano has moved away from the thumb/trigger finger shifter to more of a thumb/thumb action, like SRAM. Once I adjusted the shifter so it was more vertical, it felt better. Not great, just better. If I'm running my hand out on the end of the bar I can hook my brake lever perfectly for one finger braking but have to really contort my writs to use the trigger finger to shift. Thumb is okay. Might try running the shifter inboard of the brake lever and see how that goes. Down shifting one gear feels okay, the effort to down shift the second gear requires more force.
It shifter crisply, no misshifts. There was a bit of a plastic feel, like it needs to wear in. I tried my friends shifter that has more miles on it and it still had that feel though.
Thought it was loud. I found the 11-40 cassette worked a little better than the previous 11-36 cassette, but in all honesty it's a steep uphill climb, so it's going to suck or it's going to suck.