Yes, I have a master doc 9440. Finally got it going last weekend, since my live rock came in.
At first, the hydrofoamers made a weird sound, and did not generate any bubbles. I wasted 2-3 hours fooling with it. That's when I discovered that you can rotate the hydorfoamer, then Boom! I found the sweet spot and the bubbles came roaring out. My guess is that it was not rotating, it was just shaking, and my moving the motor helped it get spinning.
This skimmer works very well and is very powerful. It has pulled a lot of stuff out in the short time I have had it. I would recommend it even though I had problems getting it going.