Despite your claims to the contrary, some of these things were rough. Even the Intel transition wasn't as seamless as you think it was -- for a lot of code, it may have been quite smooth. I transitioned a few projects myself, but these were already projects that were running on other platforms. If I had an older Carbon based app that needed to be transitioned, with some PPC assembly code sprinkled in it, I'm sure I would've had a much different experience.
And the retina transitions were mainly tough because developers had to go back and have their finished artwork redone in multiple resolutions. If you've never managed a set of assets for a modern application, you probably don't have any idea of just how much stuff is in there. It's a lot. Now double that (or quadruple that to add support for retina iPad apps at the same time) and you get an insane amount of stuff you have to keep track of.
Yes, Apple makes a lot of things easier than other platforms (I'm looking at you, Microsoft) - but that doesn't remove all of the work needed to be done by a developer.
Any perception of how "rough" or "smooth" this will be is irrelevant.
The complaint originates from developers who spend more time complaining than developing.
Remember how "rough" it was getting native iPad apps in 2010?
Remember how "rough" it was waiting for retina iPhone apps later in 2010?
Or how "rough" it was for iPad retina apps in 2012?
Or how "rough" it was for developers to move to the iOS 7 design language?
Or my personal favorite, how "rough" the Intel transition was?
And the "rough" transition to OS X retina apps for the rMBP?
And why stop there? Remember how "rough" System 7 to Mac OS 8 was? And OS 9 to OS X?
The point is, they'll always call it "rough", and it's never as bad as they say it is.
They're always going to complain.
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********. any dev worth anything at all has their UI resources in a vector format, from there all you have to do is render (save) it as a PNg in the proper resolution. boom, you're done.
Vectors certainly help for the bulk of the multiple resolutions, but there is still need for an artist to tweak things at the extremes. This article does a great job of explaining why --
http://www.pushing-pixels.org/2011/11/04/about-those-vector-icons.html
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so say there is a UI element with 999 points....
how is that going to scale to 1.5x.
Not that I agree necessarily with a 3x mode, but if Apple did it, 999 points becomes 999 x 3x to get to pixels. No multiplying by half pixels. UIKit *always* uses points to specify size and location, and points are equal to the size of 1x pixels. So Apple could arbitrarily do any size screen if they wanted to, as long as the multiplier is an integer value.
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iOS also still uses PNGs, so if you do something "retina exclusive" you could technically make a png graphic 49px wide, which would result in an uneven scaling @3x. The math only holds up if you always take non-retina as baseline. What you have to at this point. because... iPad mini and iPad 2 are still ios7 compatible, so iOS7 still needs to be developed in the same manner.
iOS 7 is not compatible with non-retina iPhones/iPod touches, however. And in that case, apps still provide 2x images, but they no longer need to provide 1x images. Again, no uneven scaling required because the view size is defined in points, which are equal to 1x pixels. 3x mode (or whatever other mode) is simply multiplying the point size by 3x to get the actual real pixels. As long as the 3x image sizes are multiples of 3 (just like the 2x ones are multiples of 2), everything just works.
