I started with WP7 on a Samsung Focus S (coming from Blackberry), and I was in love. I continued through a Lumia 920, and still loved it. After my 920 died, I did a stint with a Lumia 535 to hold me over until the next big Windows Phone. However, the wait was long. And during that time, I began to miss out on more an more apps, and some of my primary apps (like BofA) began to disappear. When the Lumia 950 came out, I bought into the Windows 10 hype, and decided to give Microsoft one last try. However, I was sorely disappointed. The hardware and interface were still great, but the apps still sucked, and the failure to include MirrorLink support was unforgivable (especially since the only useful implementation of the much-hyped Continuum would have been in-car).
I have now switched to iPhone 6s. And I miss Windows Phone desperately. The iPhone apps really are light-years ahead of WP, and for that reason, I have to stay with Apple. But the UI sucks, and Siri is grossly inferior to Cortana. Text message over bluetooth doesn't work, and I no longer have the seamless, hands-free text implementation of Cortana. Even CarPlay sucks, because you have to see a text message notification on the screen, and then interact with the screen to get Siri to read the message (so dumb).
If anything, this was the most frustrating thing about owning a Windows Phone. Microsoft was INCAPABLE of marketing or capitalizing on the aspects of the phone that were superior to the competition. And it even abandoned many of its distinguishing (and useful) features, like hubs, and social media integration (I know, not their fault, but it's Microsoft forgodsake, they can afford to license whatever tech they want). In the end, Microsoft has a superior product, but has been reduced to irrelevancy, by its own failure to market that product. If they can't even keep their biggest fans (like me), I don't see a path forward. Though I would love to be proven wrong.