It's not just about the UI - it's the services. At least for me. After the Lumia 950 getting ****ty reviews, I first switched to BB10 to just experience the death of another good OS there. Now, a Nexus 5x is my electronic assistant, and honestly - Android looks and feels a little bit like patchwork.
How the front end is solved, I don't really care about. All I want it to be, is to be informative (and the tiles are awesome for that)
What I really miss on my Android Phone is that uniformity in services, Windows Phone offered to me. Cortana on Android is more like a sad joke, while Google Now just puts everything into the Google Account (I refuse switching to). I often used the feature to my Phone reminding me to topics connected to a certain person or place. Sure, Google certainly offers something like that - but am I able to set these reminders easily on PC and Laptop without needing to start some apps? Natively on both, PC and phone?
All CShell is giving me is hope, that MS in fact isn't letting Windows on phones die.
And regarding to the Silverlight issue - I don't like Silverlight, as I dislike Flash. Sure, there are some essential Apps written in Silverlight, but honestly - there are about 10 to 20 essential Apps you need. Why isn't MS just getting in touch with Facebook, telling them to program WhatsApp as a Universal App while covering the expenses?