OS-X and iOS are pretty much the same OS under the hood, and the latter already runs on Apple's A-series that's used in iPads and iPhones. So bringing OS-X to the same CPU, which will enable Apple to leverage the same CPU base is comparatively trivial compared to the migration of System 7 from Motorola 68k to PowerPC, or OS-X from PowerPC to x64.

Windows NT did run on MIPS, Alpha and PowerPC as well, but no mainstream software, including Microsoft's, was ever ported to those platforms, which is why they failed. In this case, otoh, apps that run on iOS should run on OS-X: only change is touchscreen vs cursor. Yeah, their authors might need UI adjustments to the software to account for going from an iPad to a MacBook

I wonder how Replicant is at the moment, and whether there are phone companies willing to bundle Replicant w/ their phones. That way, they can avoid putting in app stores that have only Google's or Apple's interests in mind. It gives non-Google app stores the opportunity to compete fairly, and the Play store wouldn't have to be preloaded. Also, for maps, they don't have to go w/ Google Maps: there are others. Similarly, they can put in any Email app and then have it automatically configure common mail services like Gmail, Outlook, Yahoo! and so on. (In fact, that would even sidestep the wierdness that email services like Gmail and Outlook have been up to lately)

Also, their phones wouldn't by default be spying devices, and would also be customizable enough for people to optimize it as needed

Well, we see how it is in the iOS universe, where the only store that's there is Apple. So one only gets to put in apps that Apple approves of, for whatever reason. It's somewhat similar in the Play Store, where Google gets to determine whether one's allowed or not.

I get the quality argument you're putting out, but that's something that the market is more than capable of weeding out. Crappy stores will find themselves shunned very quickly, as word of mouth moves fast, particularly in India. In practice, in the end, one is not likely to see more than 2 or 3 popular app stores, just like the market doesn't seem to have room for anything more than iOS and Android as far as phone OSs go. Also, having alternatives to the Play Store also means that if someone's app is rejected by a store for any reason, s/he can put that app up in one of the alternative stores.

For the same reason you don't want Amazon being the only retail store in the world, you don't want only the Play store to be the only game in town. I'd also like to see alternatives to Apple's App store as well

Aren't a lot of apps just re-jigged websites? In which case the open-source argument would be moot, right?

Also, phone and tablet manufacturers - why would they care which app stores their customers prefer, unless they have bundling agreements w/ any of them?