If it can function as well as or better than my current Nokia Lumia 1520. Before reading ahead, keep in mind that I also had the following devices in the past - iPhone 5, Nexus 7 2012, Nexus 7 2013, Xiaomi Mi 3 - and now, I got the Meizu MX4 as a secondary phone. I also consider myself as a tech enthusiast, that's why I keep bias as little as possible.
These are the reasons why I am still using my Lumia:
1.) Very dependable camera and RAW support: I had this phone since December 2013, and up to now, it still functions as my daily driver. Even though the camera lens already got a few scratches, the pictures that I take with my phone are still crystal-clear, especially when I edit the RAWs already. When people usually look at my laptop, they react with magnificence on my screen wallpapers. Little did they know that all of those wallpapers were RAWs edited from my L1520.
2.) Ease in keyboard input. The stock Microsoft keyboard is very easy to use, compared to the other OS'es. I don't know why, but this is really one of the reasons I'm sticking with my Lumia as my daily driver. I am also texting a lot on my Meizu MX4 (Android) for daily reports at work but I really have a difficult time using its keyboard. I already switched from stock Flyme keyboard to Google Keyboard and now to Swype.
3.) Outdoor use and durability. With my phone lasting for more than a year, I am more inclined to use this in my field works (as a geologist) and this phone still functions well. Aside from its ClearBlack display (which, amazingly, is readable outdoors even in the lowest brightness setting, albeit being very dim), there are times that my phone's screen meet with small touches of drizzle. Yet, it still functions well.
4.) Battery life. Most of my friends who are Android users complain about battery life on their daily drivers. Luckily, I am not one of them, because of WP's efficient OS.
5.) Updates. Another complaint of my friends who are Android users are late (or never at all) updates. Even my Meizu MX4 is still stuck in Android Kitkat, and now Google already announced Marshmallow.
There you have it. I admit there's still a huge app gap, and that's why I'm keeping an Android phone as a secondary device. But if you have noticed, I mentioned having a lot of Android devices before. I think my rapid switching of Android devices is due to the fact that those devices left me unsatisfied compared to how my Lumia functions.
I am also giving Windows 10 for Mobiles the benefit of the doubt until it launches.