Nice to know that I'm not alone in thinking highly of the platform. In addition to the features mentioned, consider also that Microsoft have an interest in attracting new customers to the platform which necessarily means that they must offer some unique features in competition. Right now, as Sabali notes, that's integration with the Windows NT kernel and therefore W8. Microsoft have always been friendly towards developers as well, and so their development tools are very open - much more so than Apple's store (but of course Apple treats you like garbage because their network is so vast) and the NT kernel means that developing an app could be as easy as learning JavaScript and HTML5 - can you imagine?! Neither Apple nor Android can offer that.
Personally, since I run Fedora on my work machine and an iMac at home, but my employer's scheduling is handled entirely via Exchange, having a Windows device has proven helpful. I've also recently purchased the Microsoft Band since I believe it to have the most comprehensive and well-realized (currently) set of sensors/biometrics and phone integration (and I needed to do some heart monitoring). Though the band is cross-platform, having a Windows Phone allows me to use *all* of its features. Microsoft have also recently opened the Band's API which will allow for greater development (possibly even my own).
Wrt. hardware, I have long been a fan of the Nokia brand and the hardware they produce. Their phones are durable, reliable and lately have featured very high quality optics. My Windows Phone is no different. It's taken some large falls without so much as a scratch.
Finally, from a privacy perspective, many people don't know that the Windows Store breaks down exactly what permissions a given app requires and asks you to CONFIRM that you're okay granting that access: that's huge! Microsoft also allow you to download free preview versions of paid apps - something Apple still don't allow (causing developers to release free versions (which are sometimes difficult to find)). The developers don't have to create separate versions to do this: the store handles it automatically.
I used to have an iPhone and I liked it. I still run Mac OS X, so I'm not at all against Apple - but I'm not a fanboy, either. I use GMail and other Google services, so I'm not anti-Google or anti-Android (though I hate their privacy record). In fact, if anything I'm anti-Microsoft/Windows. I have hated their desktop OS since Win2K, have never owned an xbox or missed their software when I used incompatible platforms (don't even get me started on their bloat).
The truth is that I justify technology based on what it accomplishes and how - not who made it or why. I like technology that respects the user and their goals, particularly if it's slick/elegant while doing so. In this case, Windows Phone has the right balance for my calculus.