I got a BB Z10 for free for being a Qt developer and attend a developer event. It was my first BlackBerry, and I am so sorry that I will have to let it go, since I am so not buying a BB device if it's just running Android (If I'll end up buying an Android device, I'll have plenty of choices). Yes, the BB OS 10 interface is a lot better for me than Android. I loved the Nokia N9, and this one was even a tiny step forward, and I'm too used to it after 5 years of happiness. I also used a Jolla for some time, and is the kind of UI where I feel at home.
The way you jump back and forth between applications on Android is really really bad for my taste. I have an Android tablet, and it annoys the hell of me that it shows lots of poor screenshots of applications that I have not opened (e.g. when I just restarted after an upgrade it shows tons of them no really running). Harmattan (Nokia N9), Sailfish OS (Jolla) or BlackBerry OS 10 give a much more useful indication of what the application is/was doing, or additional controls. Besides, you see several of them at a glance, not in a stack view that only shows a tiny slice of the second one and almost nothing of the next ones.
The top shade got one step back in the last major Android release. In an Android tablet, the user had access to different quick controls swiping on the left or the right of the screen: now I have to swipe twice to have quick access to the Bluetooth control, so moving my headset from the phone to the tablet (or vice versa) is a lot faster and convenient in BB OS 10 with respect to Android (they used to be tied in the previous version).
I'm used to not being the typical user (I'm a bit more power user, fine), but seriously, changing from one application to the other (browser to podcast to instant messaging for example) or having quick access to Bluetooth settings is something I would expect done right in 100% of the mobile OSs for this time and age.