Eclipse
I've heard of Eclipse over the years, but I've never used it before. I'm very impressed. Of course IDEs have come on since I used Visual C++ regularly many years ago. There seem to be lots of useful features and I've hardly scratched the surface. The BB10 SDK comes with the tools for deployment etc. all built in. You can even upgrade the SDK without leaving the IDE (apart from restarting it at the end).
QT/QML
QT is also new to me. You can use it without QML (a markup language for the UI) but it's nice to be able to see the visual form laid out in a file, rather than sprinkled throughout the code. One trouble with QML is that as it's not compiled but dynamically interpreted, you can make mistakes which don't get picked up at build time. It has javascript like syntax for code snippets and if you're lucky you may see an error in the log if you've done something wrong.
Cascades
This is the icing on the cheescake which means that you can develop native looking apps with another framework on top of QT. Although in the past I've hand assembled Spectrum machine code these days I want to concentrate on creating the original with my software, so it's good to have components already available, like a rich listview, or text areas that scroll. So with Cascades you get access to all that sort of UI stuff. Surprisingly I've found some bugs in what's already being used on real devices without doing too much. Maybe I've been unlucky.