I disagree: it seems clear that the CTR on the new design was 2x the old. Now, granted that 2x of a featured spot is a much bigger absolute number than 2x of typical placement. But 2x is 2x. This is a great reminder of the impact of design for anyone trying to optimize their app store presence (large or small).
I'm not sure, honestly: I imagine the differential of a new design varies depending on how users come across it. If when not being featured Dwellable mostly gets new installs from word-of-mouth, say, I bet that the new design doesn't have as much impact. (I'm sure it would still be a big difference, but maybe on the order of 1.5x instead of 2x, say.)
As they are being featured their promo art is shown to users before they get to the page for that particular app (see the screenshots for their new and old images - you can see it is part of a scrolling bar of promo images).
If they weren't being featured, the promo art would only be seen by users that clicked through to the app's page - users would only have seen the app's icon before getting the app's landing page.
So I think featured vs not featured makes a big difference to the importance of the promo art.
