Yes, it was fantastic - minimal, elegant, simple, fast, had low learning curve and everything had a description - even icons in action bar[0]. As their competitors, namely iOS7+ and Android 5+ totally replaced gradients into flat design I was very welcoming the balanced UI redesign on my Z10[1]. However, autocompletion on their touch keyboard was probably the best [2], you had 3-5 suggestion that were spread around on the keyboard and to use them I had to place a finger below and flick it up. On BB Passport it was even more pleasant with physical keyboard - it had small gesture sensor and reacted on swipes in the air above the keyboard.

On the developer side, documentation was also amazing. There are tens of full, working example applications. BB10 used QT behind the scenes (Cascades UI). It had also a Python (2.x) binary on the device among other typical UNIX programs.

[0]: https://developer.blackberry.com/devzone/files/design/bb10/i...

[1]: https://developer.blackberry.com/devzone/design/bb10/10_3_vi...

[2]: https://developer.blackberry.com/devzone/design/bb10/keyboar...