I'd like to know what it is that makes people want to leave?
Fair question, the OS is great, but still far from perfect.
Xbox music app is still underperforming and lacking basic features like proper shuffle for example even though it has been updated a number of times. MS promised regular updates and have so far been sticking with the schedule, but I personally think they aren't moving fast enough given how far back they've set everyone with the new Xbox music app.
The mail client needs a serious update and I was actually shocked that it didn't receive it as part of 8.1. I still can't attach documents and the photos I attach get resized automatically. This is with MS trying to push for enterprise...
The app situation is improving but still has a ways to to, many official apps are lagging behind their equivalents on other platforms. The facebook app that MS is working on still has a long way to go, Skype is still bulky, slow and still sucks with notifications from time to time. I'm glad we finally received a Whatsapp update after waiting for months.
I'm not trying to knock WP, I really like the OS, just being honest about its current state. As much as MS has done I still think they aren't moving fast enough to catch-up with Android and iOS.