I'm using that style of overflow and it works well! I've got both ends submerged (intake in the tank and outlet submerged in the sump), and the siphon break capped with a few small holes. It doesn't make any horrible gurgling or sucking noises like I've heard out of the other style of overflow. It only makes a little bit of noise as the water rushes down the long pipe to the sump, but you'd get that with the other style anyway.
The only thing you need to remember with this style is that you need to use the horizontal flow rates when calculating your pipe size. Also, make sure to test the overflow before you glue it - the water level will rise a bit.
Priming is easy - you don't need to fill the section in the tank becuase it fills as soon as you put it in the tank. You just need to fill up the bottom loop ('gravity drain side' in the pic). Then just suck the air out of the top loop like the traditional overflow.
One other thing - don't be tempted to swap the two top pieces on the gravity drain side (i.e. 90 degree elbow and T-junction). I did that to make it easier to prime. The problem is that the T can get swamped and possibly spill out the top. Stick with the design in the picture and you'll be fine.
