[codingvelocity]

I didn't know about Grand Central Dispatch, my experience with iOS is fairly limited.

I agree that UI is super important, but personally if i find an app is chewing up my battery it's getting removed regardless of its utility. I've also helped a handful of ordinary users diagnose why their battery life is poor. The result is commonly a poorly optimized/buggy app which they uninstall. A dead phone is a useless phone. My experience is primarily android so your mileage may vary on other platforms.