It's just to the point where I've become so invested / spent so much money in the ecosystem it doesn't make sense to switch to anything else. I stay with it for the UI; the (getting better) integration with Mac OS. It's comfortable; I know it and it's reliable.
CAMERA: 8MP, LED Flash and takes acceptable photos. Lumia Camera app has a burst mode which was removed in WP10, and is better than anything I've found third party or even in another eco-system.
BATTERY: At a stretch, it could last two days without charge, if not over used.
LAG: One of the great things about Windows Phone is that there's no slowdown, no real lag to speak of. Everything happens pretty fast.
Why I like it: This could be a long post.
APPS: There are hardly any apps for Windows Phone. Even fewer, as time goes on. Before christmas, Amazon and Ebay pulled their WP apps, and more companies will probably follow suit. Why is this a good thing? Apps are a Distraction. I don't have a hundred apps on the phone, so I don't waste time on it. I tried android for a while, and I loved having apps for every service (not to mention better quality apps for a lot of things), but after a while I realised I was spending vast amounts of time playing with apps when I could have been doing something productive, or spending more time with family. Maybe this could be solved by personal discipline, but Windows Phone just takes away that temptation
PINNING: I firmly believe the tile interface is a better mobile UI than icons. pinning things to the screen feels so much more natural to me than creating shortcuts on android does, even though they may be very similar. Tiles just present more information, look nicer, and can be arranged more neatly
ONENOTE: The OneNote experience on WP is better than android. I have about 6-7 pinned OneNote pages which I use as todo lists, to write down ideas, plan code, compose messages and more
BATTERY SAVER: Battery saver mode on WP is very effective. knocking it on stops apps running in the background and polling services, and extends the battery life by days, if necessary. It also has one very neat trick on the 925: with battery saver enabled, the automatic brightness drops to almost nothing when in darkness. This means I can use the phone in bed without blinding myself in the dark.
KEYBOARD: Mobile keyboard is better than the stock android ones, does slide typing like a pro. very nice to write on.
SPEECH RECOGNITION: This is an odd one. WP8/8.1 only allows speech recognition on the SMS app. I found it to be more accurate than WP10 speech rec which is on any text field. It's annoying that I can't use it everywhere, but I like that it mostly knows what I'm saying AND automatically puts in punctuation when I pause. Occasionally I'll compose an SMS to nobody and then copy/paste the content to email or telegram
(on a side note, Android voice recognition is pretty good too, but has serious puntuation problems. it expects you to say "period" / "question mark" / "comma" / "exclamation mark". Why on earth they don't put 4 or 5 buttons for punctuation on the voice recognition keyboard display is beyond me, it would make the experience SO much better)
DEVELOPMENT: If I want to develop a new app for the phone, I can build one in Visual Studio in Javascript/HTML. I don't have to use some framework to achieve this. My app is written and executed as HTML/JS. I can stick any JS library I like in there, use CSS to style it and web-fonts if I like. I can boiler-plate an app and have it installed on the phone in minutes. I know that android coders can code a Java app just as fast, and iOS gurus will be able to knock together something in Objective C, but I like that I didn't have to learn any new tech to write an app that works on my phone
BUILD: I drop this thing at least once a day and there's barely a mark on it. It just keeps on ticking
Ok, I'm rambling. I'll stop now.
TL;DR; Lumia 925 is a solid phone with a decent camera, and Windows Phone OS eliminates the distractions of 'having apps' =)
The killer feature for me is that Windows 10 Mobile (or Windows Phone) is just a better user interface than classical WIMP. I also like OLED displays (a requirement since WP 7.0).
On the other hand, what I miss about Android (and it is not the lack of security updates) is the ability to install crazy developer tools. The old Android has J, Forth, Clojure, Ruby, Python, and probably something I've forgotten...oh, it's GNU Octave. On the other hand, if I want to play with those things I've got my old phone.