It's easy to use, and pairs beautifully with the unintrusive perf tool, which makes the combination a joy to use.
And, if combined with a codebase opened in QtCreator, you can click on a hotspot in the flamegraph, and it will bring you automagically to the correct file and line in QtCreator, without any explicit linking required between the two programs. I discovered that feature accidentally, and the fact that it just worked seamlessly really impressed me. (Tested on a Debian-based Linux).
A big thanks to KDAB for making this tool available to us!