I got one of these a couple of years ago as it seamed a neat idea being able to move the radiator to the case edge.
However I recently discovered that they have a major weakness, and nothing to do with leaking.
The pump went, and in a discussion on the coolers forum, was told that 2 years was considered good lifetime for the pump and suggested buying a new one.
The problem with the pump going is that
1) the cpu heats up quickly as there is no actual heatsink attached to the cpu. With a decent sized heatsink you get the time it takes to heat up the heatsink and if there is a bit of airflow, some passive cooling.
2) You need to replace the whole unity, usually with a fan, I've been able to get it going again with a bit of cleaning and maybe a drop of oil, and if that fails just get a replacement fan.
I've seen a few threads talking about leaks in the past and how they've taken out other hardware (usually GPU's). If you hang around overclocking/hardware forums long enough you'll see the threads pop up from time to time. Of course they only represent a tiny portion of all units sold, but it certainly can happen, as can pump failures mentioned in the OP.
In space critical environments AIO's are a good solution, but if you have a nice big case then I'd take air cooling anyday. Those huge air coolers often very very close to the best AIO's for performance, often at better noise levels and cheaper prices. But in small cases then AIO's can really excel, albeit with the small risks that come with any watercooling.