I haven't worked on a "proper" watercooled setup since the earlys 2000s when I was setting up my own rig.
Recently had a customer approach us with one and as business is slow I couldn't say no.
his build was about 4 years old and the pump had failed so we had to completely drain the system and refill it, but it hadn't been built or designed with a filling loop, as it was 4 years old I decided to do a full system flush as well, so pretty much stripped the entire thing down.
Spilt water a few times and had to mop it up, (inside the case as well)
Definitely confirms to me that as nice as it looks, and as good as the temps are, any kind of system maintenance becomes a hassle, and this was with flexible tubing, god knows how the guys carry on with the hardline stuff.
also the price!!! I priced up a simple system with GPU and CPU blocks, 2 x rads, and a pump obviously, it came to about £800/900.
Back in the old days where air cooling was all 60/80mm fans and hella noisy it kind of made sense, but nowadays with AIO coolers or even decent air coolers and 120mm/140mm fans, temps and noise levels are comparable, overclocking is pretty much dead now as well, you are looking at very minor performance increases for potentially damaging an expensive CPU, again going back to earlier CPUs 50% increase was not uncommon.