I purchased Shimano Deore XT M8100 set a few weeks ago. I’ll report back when I receive mine.

https://a.aliexpress.com/_m0mpiRG

• The derailleur pulleys are different sizes: 12 teeth on the guide pulley and 14 teeth on the tension pulley. They also run on sealed bearings and spin freely which is nice - one thing that really irks me about 105 is that Shimano uses pulleys with only bushings and they always seem to gum up.
• The thumb shifter is matte plastic rather than glossy, and it doesn't have any branding on it. I like this - it's grippier than a glossy coating.
• Both right and left brifters have retention clips for the hydraulic lines that prevent them from swiveling outwards. The clips are retained by two 2 mm screws in the rear of the body; when they're unscrewed the clip can be popped out and the lines can swivel outwards for easier installation if the hydraulic lines foul on the bars. But if the lines don't foul, I'd actually keep the clips in because they retain the nut so you only need one wrench to install the hydraulic line instead of two. This seems to be different than previous versions, or maybe just the carbon version? See Trace Velo's video here: https://youtu.be/NKNcKwiH6v0?t=928 where the nut seems to be held captive by the shape of the brifter's body rather than a separate retention system.
  
  
  
  
• The shift lever has a 1.5 mm grub screw at its base which adjusts the shift paddle position independent of the brake lever. There's a ridiculous range of adjustment, way more than would ever be realistically used, but hey it's there anyway.
  
  
  
  
• I screwed in the free stroke grub screw to see if I could replicate the rattling issue, and I wasn't able to, but maybe this will be an issue when the brakes are all set up.

• The brake bleeding process is exactly as depicted in the official bleed guide video on youtube. I used the same EZmtb brake bleed kit that Trace Velo used, which has the adapter needed to screw into the caliper. The brake lines and brifter bodies came filled with light blue oil, which I flushed out and replaced with shimano mineral oil. Really easy bleed, no more difficult than any of the shimano brakes I've done. I did unscrew the free throw adjustment screw before bleeding; after the bleed was done the brakes were firm but needed to be pulled back quite far to make contact with the rotor, and screwing in the free throw screw about 3 turns reduced the throw a lot while not negatively affecting rotor/pad clearance as far as I could tell (no rubbing).
• I used a housing ferrule with a plastic sheath to protect from the sharp edge on the cable exit of the rear derailleur as depicted in tsneidin's post previously. The shift indexing is VERY sensitive to cable tension; a quarter turn of the barrel adjuster yields very noticeable differences in shift performance.
• The b adjustment screw on the rear derailleur is almost useless. I'm using a 46 tooth cassette and have the b screw backed out almost all the way.
• The clutch isn't as strong as the ones on Deore or GRX rear derailleurs, but still seems adequate for a 1x setup. It's certainly stronger than the first gen Sensah SRX clutch which dropped my chain quite a few times.

• The brifters are quite petite. I have average sized hands and if the brifters were any smaller I wouldn't be able to get my entire palm on the top of the hoods. The shape is quite nice though, and there's support in the brifter body everywhere there's contact with the hand or fingers; overall quite comfortable.
• The braking is excellent, easily on par with the 105 disc brakes on my other bikes. I haven't experienced any rattling from the brake piston retaining clip either.
• The force required to downshift is greater than upshifting, and I often have to use 2 fingers to comfortably downshift. The downshift lever/paddle has a moderately thin section near its top and I'll be keeping an eye on that section for any signs of fatigue.
• The ability to dump 3 gears up + 4 gears down is amazing, I use it quite a lot when slowing down/speeding up or cresting a hill. Probably my favorite feature to be honest. It is hard to dump all 4 gears with the thumb shifter from the top of the hoods, much easier to do in the drops, but I can get 3 gears reliably which is enough for me.
• I'm temporarily using flared bars (~16 degrees of flare) until the actual bars I ordered arrive. The brifters are ok at an angle but I think they'll be more comfortable in a level, non-flared position. Something to think about when choosing bars, as this is nominally a gravel groupset and all gravel bikes seem to come with flared bars these days...
• The compression nuts on the brake calipers seem to be anodized so I don't think they'll be susceptible to the corrosion problems that Trace Velo had. I do live in a much drier environment, but I plan on riding this bike quite a bit in the winter so it is a concern.