I’ve been using AIOs for awhile.
I like my computers really quite and I find that an AIO with low rpm fans can cool a couple very well with little noise.
Also partly I switched over from air cooling when air coolers got ludicrously heavy. Once you’ve got the radiator installed it’s way easier to work around an AIO cooler than the mahoosive air coolers that way a Kg or so and block access to most of the motherboard.
I suppose that pump failure is a thing but I’ve not had it happen to me in the several years I’ve been running AIOs plus even if the pump did fail all that’s going to happen is the CPU is going to throttle and I’ll get some temp warnings, nothings going to be permanently damaged.
Now I guess a water leak is genuine issue if it happens but I’ve never met anyone that’s actually had that problem so it’s not something I’m going to worry about. It’s not like AIOs are pressurised system!
Honestly they are great at cooling, very quiet, look nice (if that’s your thing) and easy to work with. There’s not a lot not to like!