I like it so far. The one I bought is 6' tall and is designed for a 15" culvert. It comes with an assortment of 5" and 7" "stoplogs" that are inserted to set the water level. It turns out that you can get to almost every whole number by adding combinations of 5 and 7, so you can set your desired water level at any level you want.

I see a few other potential benefits from it as well. First, the water that is leaving my pond is coming from about 5-6' below the surface, therefore I'm not losing the most oxygenated surface water. Secondly, I can very easily lower the pond level by up to 5-6' for maintenance and don't need a pump to do it. All I would have to do is remove the stop logs one by one. Unfortunately a siphon system wouldn't work for my set up, although I understand that is also a popular choice for lowering ponds.

The only downside I can see so far is that it costs more that what a simple culvert at the surface level would cost.