First of all, I won't be bribed by the promise of unlimited downloads if I will give a five star rating and write a good review. That should not even be allowed by Apple. And a PAID PREMIUM app should include unlimited downloads, anyway. (I received this same bribe offer with the unpaid app.)
This is nothing more than an aggregator and they're not especially particular about what they aggregate. Most pics were medium resolution with some being low. I found not a single HD wallpaper. The search function returns few to no hits, even on searches as broad as "military" or "India".
The only thing you get for your money is a mediocre app that is ad free. I guess that's saying something, though, given the fact that the ad supported version had so many ads that it was practically unusable.