This is a great skimmer, as long as it is properly maintained. The venturi seems to get clogged fairly easily, but is also very easy to clean. IMO it is much better then a Remora Pro, which I also have. To keep the turboflotor running smoothly, just take a cup of hot water and let the venturi suck up all the water. Do this once a week, and it'll dissolve all the calcium and salt buildup in the venturi and run like a champ.
Yes you can gravity feed it. If you do, you'll need to tee off your drain and add a gate valve (not ball valve) to control the amount of flow going through it. I like this setup better then feeding it with a powerhead (mj600 recommended). One less pump in the system, and the water the overflow pulls is usually dirtier (i.e. the surface film goes directly to the skimmer).
BTW, get the one with the RIO 2100. And I have heard no reported cases of this RIO pump melting down in non pressure rated applicatione, only when continually turned on and off w/wavemakers, and used as a return pump from the sump.
danny