iOS 9 was very buggy also upon release and frankly it still is.
iOS 9's bugs are a far cry from what I'm seeing with Windows 10. Apple has been smart enough to leave the core experience largely untouched. And while they're slipping, the OS still feels polished. Microsoft, however, decided that they needed to overhaul every little thing and in far too many cases, for the worse.
The problems I'm encountering aren't bugs for the most part. It's a widespread of lack of polish and changes that don't improve the experience over what I had in WP 8.1. The OS doesn't even get the basics right. Touch is extremely twitchy, even on the home screen where it occasionally misreads swipes. The difference is glaring compared to my Lumia 920 which offered fluidity and precision comparable to an iPhone.
Sadly, every time I lean towards keeping the phone I encounter a new source of frustration; the latest being Cortana's awful new web search and a ridiculous inability to save images from that search like I could previously.
It seems that Microsoft allowed feature creep to spiral out of control and decided to cut their loses when they realized they weren't going to meet their deadline. I also wonder if Microsoft outsourced the entirety of Windows 10 for mobile. It's got that sense that while everything works to spec but nothing feels quite right.
Perhaps the strategy is to bide time until Surface Phones arrive next year. But in the meantime I don't see how the platform isn't going to do anything but hemorrhage users. And that means that the platform gap is going to persist for the foreseeable future.
It pains me to be no negative because I really want to support the platform. Frustratingly, for a platform that was supposedly intended for the fans it feels more like an insult.