Jesse I don't have any experience with that model but I was just looking through the new Advanced Aquarist book and it had a couple of articles on skimmer efficiency. One of them evaluated the different skimmers including the downdraft ETSS and it seems the results showed it to be much better than for example the Euroreef and a couple or others.
Seems like a really good skimmer. I have a top down injection Elos and like it really well.