I have one and i love it!
But what has been said is basically true. They are not good skimmers. You can make them quieter by using a longer peice of tubing for the air intake. These skimmers do work but they underskim and thats what i love about them! I dont use a skimmer at the moment but if i had to use one i would prefer to use one that underskimmed rather than overskimmed. This is personal preferrance of course and works for the system i run as its 100% natural (including the seawater). Undreskimming tends to keep much of the unique qualities of seawater in rather than stripping it.