I have only looked a little into the AiO water cooling solutions that are out there. I know enough that I am waiting until the market diversifies and/or improves by a marked amount. We'll see what is around the corner, but, even then, I think by the time I get to the point that I want to convert, I will invest in a custom set-up. It's just my tinkering nature.
Until then, I feel a lot more safe with air cooling. The only thing I need to worry about failing is the fan, and I have plenty of spares - I love to experiment and see how things work.
Of my collection, I currently have the Enermax solution, an Arctic A30 Freezer, and a Be Quiet! Shadow Rock 2 that I run tests on with my two rigs. This investment will be my first high-tier purchase, so I'll get to see how much better it actually is over those entry-level solutions. I originally wanted to get a dual-tower air cooling set-up, but the Be Quiet! Dark Rock Pro 2/3 was too expensive, and the Noctua NH-D14 too overdone. (The Thermalright Silver Arrow and Phanteks PH-TC14PE would not fit well with the combination of my RAM and case.)