And that's pretty much what's happening with WP7. Windows Phone users are getting an upgrade [1], but it won't be as fully-featured as WP8. Apple just did the slick move of calling both the partial update and the full update by the same name.
So you get a new UI; who cares? What is truly important is application compatibility, and someone with a 3 year old iPhone 3GS will still be able to run brand new apps made for iOS 6.0. On the other hand, someone in a store buying a Nokia Lumia phone today might not be able to run apps released 3 months from now.
So in other words they give you both the option to retain current performance and the option to upgrade and reduce performance but have better app compatibility, and that's somehow a bad thing?
Software updates don't have the ability to give your device more RAM or a better processor, and the original iPhones were extremely underpowered. I don't know exactly what you would like for them to do.
Let me guess, you probably had an original iPhone and suffered when iOS 3.0 came out and performance was terrible, right? Did you know that a subsequent release (3.01 I think) fixed this issue and performance was fine again?
The one thing that I will acknowledge is that newer devices with more memory and more CPU power tend to go to app developers heads and they start to write apps that run beautifully on new iOS hardware, but slowly on old hardware. That is hardly an Apple problem - you'd be hard pressed to find a 3 year old PC that can run the latest high end games as well as a brand new one.
I personally find it amazing that my original iPad purchased 2 years and 3 months ago will still run the latest software just fine. My wife's iPhone 4 purchased 2 years ago also works just fine, and she didn't want to ugprade to the 4S because everything still "just works" for her.
With each version of iOS, developers can access new API on older devices. With Windows Phone 7.8 it will not be possible to access shared native API set.
So would it have helped if Microsoft had been ingenious like Apple and called it Windows phone 8 but delivered fewer features instead to older devices?
No it would have helped if Microsoft had provided the WP8 update instead of just a UI tweak. Spiffing it up to look like WP8 solves only a cosmetic problem, it doesn't allow WP8 apps to run on older devices.
In a major update like WP8 or iOS 6, APIs are depreciated and new ones that are exclusive to the newer OS are introduced. Having everyone on the same version helps developers target much better.
If you think iOS 6 for the 3GS is just iOS 5 with UI tweaks applied, you're dead wrong. It's iOS 6 with features disabled so it will run better, not iOS 5 dressed up to look like iOS 6 which is what MS has chosen to do here.
And that's pretty much what's happening with WP7. Windows Phone users are getting an upgrade [1], but it won't be as fully-featured as WP8. Apple just did the slick move of calling both the partial update and the full update by the same name.
[1] http://www.slashgear.com/windows-phone-7-8-brings-wp8-ui-to-...