I'd like to add nzbclub.com to semels incredibly good list. I've come to the same conclusions

It's not only retention that plays a large factor, but also the results themselves (of course) and nzbindex gives considerably better results than binsearch.
Not sure on nzbindex vs nzbclub. They both have great retention but I'm not sure how they compare in regards to accurate and complete search results. (And removing junk posts)
I never see NZBclub mentioned anywhere, so it appears to be my secret. Now it's.. not
Sorry to go a little offtopic here, and maybe a fit too ahead for a concept.