it seems very similar to LXQt and the project it replaces when it comes to resource usage and useability, except it is more mature and support a few more things.
Thats basically what keeps me on KDE. I would think KDE should disable akonadi and stuff by default personally - its super useable without all the heavy weight "crap".
Alt-F2, konsole and kwin basically are the reasons I use it.
Here's an example, too: I can tile my windows on any desktop i want with kwin without sacrificing non-tiling windows. I can even mix tiling and non-tiling. I dont have to remember 20 shortcuts for this, it works with the mouse too. Basically, its seamless.
(Thats also why I use it over awesomewm for example)