(and risk pump failure and higher temps than top air coolers).
Pump failure could certainly be a possibility.
Higher temps than top air coolers is pretty much BS.
When properly configured the H50 will cool as well as almost any air cooler., except maybe the DH-14, have you seen the size of that thing ?
This is a review done by a watercooling guru, pay close attention to what he writes in the " Final Thoughts and Conclusions " http://www.overclockers.com/corsair-hydro-series-h50-review/