I had an M8/114 Limited for a week (loaner) and loved it, but wouldn't spend $30K+ knowing that it might spend more time in the shop than on the road. After 17 years of production the TC was a pretty reliable platform with a few mods and a little preventative maintenance. Shouldn't have to do anything (read Goldwing), but that's the way it is.
HD should scrap the M8, take their losses and bring back the TC!
While I know they can sump, and some will for sure, maybe all will under the right condition.
That said of my 4 110 Twin cam CVO touring bikes, 2 had lifter failure. One had two compensators, one had hydraulic clutch failure. One never had a chance as I built the motor with 1500 miles on the bike, Had the heads done, beehive springs rather than HD's to heavy springs, and much better lifters. Both lifter failures occurred with over 40K on the bikes, on still in warranty by 2 days, motor replaced with 44K on the bike, the other was 46K miles.
I'm on my 3rd CVO M8. I put 21,500 trouble free miles on my 17 CVO Street Glide. I put 24,850 miles on my 18 CVO Road Glide, trouble free. Took two 5000 plus mile vacations on it, on to Glacier in the Summer and the Other to AZ, NM and South TX in Sept. I now am on a 19 CVO Road Glide.
My bike are ridden, and pretty hard. On the way to Glacier, first day I rode 1065 miles in 14.5 hours. I also did a Iron Butt, 1500 miles in 33 hours on it. Then I did 980 in 13 hours on my way to AZ. I also push it hard in the curves.
Maybe I have been lucky with the sumping.
I think it is a better engine, makes more power, runs smoother.