I'm pretty sure that if they're in anyone else's good graces, it's because they provide a great product with solid service at a decent price. It's absolutely not because they had to bribe people to overlook the fact that they weren't really any good.
In essence, DF is an endorsement-based model. This is one where a justifiably trusted source uses their hard-won credibility to promote products that reinforce their credibility. It's pretty much the opposite of a model that allows people to "buy their way in". Indeed, that's the whole point. You can't buy your way in. If you don't have a decent product, you're not getting listed.
I don't think there is anything extremely unscrupulous going on, just that there isn't much of a wall between editorial and advertisement with Gruber's model as some people claim.
[1] http://daringfireball.net/feeds/sponsors/2014/01/cleanmymac_...
Just wanted to second your comment and add that Everpix too was also a really good product before they closed down (I still haven't found an alternative that works for me).