I just closed darktable few minutes ago, so I guess that made my experience of it pretty fresh.
On my system (Ubuntu 17.4), darktable runs nicely. And it's easier to use than RawTherapee. I only encountered some problems cause it to freeze up when loading photos, but I can't figure out the reason (Of course it's not because I'm loading photos).
RawTherapee is bit harder / complicate to use, but once you used to it, they're almost the same (Not totally, like darktable's Vibrance adjustment is far weaker than RawTherapee's etc).
One problem with RawTherapee for me is, it sometime can't correctly recognize the color profile of my camera, so the initial preview look over exposed and require manual adjustment. I didn't get same problem with darktable.
One of the reasons I use RT is because it doesn't try to take ownership of my images. I have a hierachy of images that looks something like this:
Images/
Images/2017
Images/2017/10
Images/2017/10/01-jody/
Images/2017/10/01-jody/RAW
Images/2017/10/01-jody/JPG
Images/2017/10/01-jody/JPG/thumbs
Images/2017/10/01-jody/Public/
I like that I can file things my own way, and use the tool just to export from .CR2 -> .JPG.Having used both Dartable and Rawtherapee, part of the reason I primarily use Darktable is that it seems to better facilitate working through a few hundred images in a few hours...a use case that not everyone has and that some people might reasonably not ever wish to have but one that I deal with based on the type of subjects I sometimes shoot.