With all due respect to those who do use the turner app, it is a waste. For those of us musicians who would use such a thing, either we have a decent enough ear we can tune it ourselves, or we have tuners. Why pay extra for something that stupid?
Not quite sure I follow here...not everyone has perfect pitch and even though I do I still like having a 7 octave chromatic pitch pipe in my pocket at all times since I can still be a few cents off from 440 and a peeve of mine is hearing guitars in tune with themselves but not with others. Overall having a metronome and pitch pipe (ironically the tuner is the weakest part of the tuner app) on my phone is worth 20 bucks for the convenience. Though I think that is subjective, it would depend how much the musician is traveling.
edit: just so I am somewhat on topic, I would not mind if they released this app for free, it is more of an insult seeing them try to charge for it. Clicking a weather app from my main screen would be a nice convenience but not one I would pay for. They could have released this as a "thank you" (I can't imagine that either) and instead of another negative opinion to add to the list it could be a positive.