I have been using one for almost 2 years (LG 4MDSX) and love it. Of course I use it to return water from my sump in the basement, so I cant hear it at all by the display tank upstairs.
Some people will tell you that they are noisey pumps but even when I am down in the basement, the water running in the sump and my protein skimmer create way more noise.
They also tend to run warm (even hot) to the touch, but I asked the manufacturer and they said that was normal. Besides, all pumps create heat and I would rather have it go into the motor housing and into the air then into the water.