Really one of my favorite pieces from my my new drive train. I spent a year using the previous gen GX shifter and this is a significant upgrade. The internal bearing as opposed to busing makes for a much crisper shift! Sometime I feel like this thing knows I want to shift before I do. Very intuitive and ergonomic. Pro tip: If your'e riding in the rain a lot or snow biking, cut a little piece of skate board grip tape out in the shape of the trigger and you will never slip your thumb again.
I have only been on the SRAM EAgle X01 Eagle drivetrain for a few weeks though I am enamored with the performance to this point in shifting and gear ratio. The shifter plays a huge part of it as it is a brainless setup and tuning with a crisp single shift up or single/double shift down while being easy to place on the bars. The only thing I'll be doing is putting grip tape on the knobs and then letting it do its thing when I need more speed or climb-ability.
1x is the way to go for mountain biking. I cannot tell you when the last time I dropped a chain was (I do not run a guide either) When I was running 1x11 I always ran a 28t chainring. I am not a stellar climber and needed something I could slog up the mountain for 2 hours of straight climbing, and I am not a world cup enduro racer, nor do I care if I spin out of gearing on some fire road descent. There were only a handful of trails, or sections of trails where I could have used a taller gearing so that I would not spin out. Enter the Eagle! I run my eagle drivetrain with a 32t chainring, which gives me slightly easier gearing than my previous 28x42 setup, but I have yet to find a section of single track where I could run out of gears. I could not see running a 30t chainring with Eagle unless you are longing for the gear range offered by the old school 3x drivetrains. I love the responsive and consistent shifting that Eagle brings to the table as well. Well done SRAM, looks like you are always at least a step ahead.
Eagle 12speed is not what I would call a game changer, but more of an evolution from the original 11speed 1x system from SRAM. The broader gear range that includes the 50t ring in the rear allows me to run a larger ring up front and still have a big bailout gear. The X0 trigger shifter offers lightning quick shifts that are crisp and firm.