I've been with WP for seven years and have loved every moment of it. In my opinion, W10M is the most crisp, quick, and slick version of Windows. It's not 100% perfect, I really wished this current version of WP was a mix of W10M and WP8.1, but it's still excellent as it is.
The app gap never bothered me. I don't need Snapchat to talk or do whatever people do with Snapchat (I assume they take pictures and send them to each other? I can do that with the texting app or just use Facebook). Speaking of Facebook, the W10M FB app has worked flawlessly for me. It was watered down and buggy with the previous OS versions, but this one is damn near perfect in my opinion. I don't use NFC or any wallet type of program to make payments, I don't necessarily trust them. I'm perfectly fine paying things the old fashioned way. I don't care if my bank doesn't offer an app for my OS, the site loads and looks great in Edge. Any other apps I need, I have. Any apps that aren't available are made by third party devs, and most work well. For instance, once Google blocked Microsoft's use of a Youtube app, I found MetroTube. It's a great third party Youtube app that lets you download videos, play audio when the screen is locked, and the UI of the app looks and feels great (aside from a few glitches I've seen in the past, but I haven't noticed them at all lately).
I've dabbled with Android and Apple in the past (my ex's S3, Mini, 4, 6, 7 and a friend's iPhone), and I hated all of them immensely. Clunky UI, important settings hidden and not readily accessible, extreme glitches and lag, rebooting, viruses, hacking, and general disorganization were what made me realize I made the best choice by sticking with WP for all these years. I had some of those problems on WP but not near the extent I had found on the others. In fact, my ex who was a diehard Galaxy fangirl once told me she was jealous of my phone's seamless functionality. The app gap was the biggest problem for her, but she liked the live tiles and thought the UI in general was superior to anything Android had to offer.
I'm using an Idol 4S that I picked up last Friday (upgraded from my beat up HTC One M8) and I'm in love with this thing. It's not quite been a week yet so I know I could be in for some disappointing behavior from it at some point, but so far it's a rock solid performer. It's clean, it looks absolutely beautiful, and it works amazingly each time I use it. I've gotten the Incipio dual hardshell case (with the rubber inner casing) on it and it looks damn sexy. It hasn't been long, but experience with it has put it as a major contender against the 1520 as my favorite phone ever.
Of course I'd be heart broken if Microsoft dropped the hatchet on WP altogether, but I wouldn't leave. I don't need to. It's not like my Idol 4s will suddenly shut down forever once support is dropped. The phone is stellar and so is the OS. It's absolutely fine the way it is. I'm hopeful that MS has something in store for us pretty soon, and my gut tells me they do. But either way, I'm fine in my own little world. Yall have fun jumping ship.