Sadly it doesn't have what it takes to be a very effective quiet CPU cooler by SPCR standards. Compared to most recent large tower heatsinks we've tested, the H50's thermal performance is close to the bottom end of the spectrum whether paired with the stock fan or our low speed reference fan. The H50 may be a victim of our open testbed which we prefer because it eliminates several variables impacting CPU cooling performance, but even if it cooled as well as the Megahalems of the world, the noise of the pump would remain a problem. The pump generates a loud buzzing sound like that of a toy motor, so no matter how well the H50 performs, in a closed case or otherwise, it will always be louder than a traditional high performance air cooler unless you use a loud fan to drown it out. Furthermore, the H50 lacks a soft mounting option for the radiator and fan, so vibration may also have an additional negative impact on its overall acoustics.
While the Hydro H50 is an affordable single-piece water cooling solution, it is still on the expensive side compared to most high performance heatsinks. Ideally a CPU cooler should have a good balance of performance, noise level, and cost. If you judge the H50 on any two of these criteria, it fails to make a splash.