I recently learned that if you live in a place where Citroën LHM is readily available, it's a less-expensive and compatible substitute for Shimano mineral oil brake fluid. Conversely, if you're in a place where LHM isn't available for love or money, you can substitute Shimano mineral brake oil instead of going on a wild goose chase of the Citroën product.
The components range from OK to outright crap and the labor to screw around with them easily adds up to a significant fraction of the cost of the bicycle. What would've been a 15-30 minute cable and housing job can easily turn into a 60-120 minute hose and bleed job. Assuming you have the parts on hand to terminate the hose on both ends, that is.
In 10 years, there will be an absolute glut of bicycles that are basically fixable except for their totally unsupported hydraulic brakes.
The braking performance ranges from better than the equivalent price-point rim brakes to absolute crap. I hadn't ridden my mountain bike for a while, and was pleasantly surprised to realize that the 20 year-old Avid BB-7 cable-actuated discs on it compare favorably to most of the hydraulic systems on the market.
Good hydraulic disc brakes are just so good.
Sadly I need them more, I’m a chicken on the decent and there is a lot more of me to stop.
I think hydraulics are overkill for bicycles, but apart from that what's the problem?
They get contaminated fluid - presumably from shit cylinder seals. They can be difficult to tune (too much travel, not enough). They can be fiddly to change pads. The pistons stop working on one side (binding up), they can leak, etc.
Combine all that with an electronic, wireless gear shifter that’s in close proximity and the roadside repair in the rain can be miserable.
Don’t get me wrong, I like them a lot but most my shop visits are for brake repairs. I have to work on them every few weeks as I go though pads in as little as 6 weeks.