Well, here's my input.
I was running a Reef Octopus Extreme 200 (90g DT/30g sump) for a year and I swapped it out for a NAC7 last week and so far I'm very happy I did.
My main reasons for changing skimmers are these:
1) NAC7 has a small footprint in my sump. I can pull the entire skimmer out of the cabinet without any issues. The Octx was a pain to remove, I had to take several pieces off and then work the skimmer body out of my cabinet which typically led to me spilling water on the floor. I've learned that if I can't easily get stuff out to get cleaned, I'll probably slack off on cleaning it.
2) Wow the NAC7 is very quiet compared to OctX200. The tank is in our family/TV room and the noise from the skimmer was a bit annoying. Now with the NAC7, I can't tell it's on unless my ear is to the cabinet door. The overflow and MP40 (a different issue

) are what I hear.
As for performance, my skimmer is still breaking in but I think it's comparable with a slight edge to the Octx 200. I knew this might happen but points #1 and #2 were my main goal.
FYI, my tank is lightly stocked with 2 clowns and a Kole Tang and mostly softies and LPS. In the future, as my population grows, we'll see how the NAC7 holds up. Otherwise, I'd love a Reef Octopus XP-2000sss (about the same footprint as NAC7).
Now if I can only quiet down that MP40
