I changed my hardtail from xt 2×9 to xt 1×11 about a year ago now and my thoughts so far are that there are more negatives than positives about it.
I like the simplicity of only one shifter and single ring up front and it’s lighter, although in reality a couple hundred grams doesn’t make much difference.
Dislikes are that compared to 9 & 10 speed everything has worn out twice as fast, the top sprocket of the cassette is made of cheese compared to the rest of it so you’ll be replacing a good cassette due to wear on one sprocket, everything costs twice as much to replace as 9 or 10 speed, chainline is crap in some gears which probably contributes to the wear issue, once the chain ring starts wearing the chain will keep falling off (my last narrow wide ring lasted only 250 miles!), i don’t like the big gaps between gears higher up the cassette as it always feels like you’re in the wrong gear.
I’m sure it suits some people and sram 1×11 might be better but for me the 2×10 xt drivetrain on my full suss is far better.
Edited to add 99% of my riding is done on the Quantocks which is like grinding paste in the wet hence wear being a big issue for me