I have one in my African Clawed Frog tank. I wouldn't recommend it for anything that needs deep water. In fact, I have mine up on a platform in order to make the water level deeper. Even on the platform, the water's somewhere around 8 inches deep. I could raise it another inch or two to the 'max depth' line.
Debris also seems to concentrate in the area before the filter pads. I suck it out with a turkey baster every time I clean the tank.
Overall, it's decent enough, especially if you have a tank that's not heavily stocked.