I'm glad someone has written about this because it's something I've noticed over the past few OSX major releases. The interesting thing is that speed and stability appear to have been getting better for my use cases. However for the first time in my 20 years as an Apple user, this has been at the expense of visual fidelity. Both iOS and OS X seem to be slightly "glitchier" and applications end up in bad states where the only clear path to a fix is relaunching.
Not to be a stickler, but this particular part of the discussion seems unfair to me. Application bugs should be blamed on the app developer, not on OS X. (Unless, of course, it's one of Apple's built-in apps.)
