While Apple's software quality has never been perfect, it certainly feels like it's been trending more negatively than positively in the past several years, sin

While Apple's software quality has never been perfect, it certainly feels like it's been trending more negatively than positively in the past several years, since Tim Cook took over and Forstall [left / was kicked out]. My guess is that it's largely a sin of omission: Apple has such a strong drive to add features and keep pace with Android, that fewer resources are marshalled to do purely internal improvements (iOS 7/8 badly needs its Snow Leopard iteration). They've also been even more focused on hitting arbitrary release dates (as driven by events and new hardware) which is never a good formula for reliable softare.