I have tried out darktable a few times, and don't like it. As a point of reference, I use Capture One about 95% of the time, and LightRoom the other 5% of the time.

Aesthetically, the darktable GUI is not as polished as C1 and LR, and is less responsive. In some cases, tools and controls that have fairly standard interface conventions in other imaging software are different in darktable. The UI is generally less intuitive than C1 and LR.

On the technical side it does better, but can't compare to C1 and LR. A lot of the controls are difficult to use, and the effects don't seem as "smooth" as C1 and LR, if that makes any sense. It's also a lot slower, and I'll often make an adjustment and have "working..." show up over the image while it chugs away. And I mean for simple stuff like adjusting levels and exposure, that take effect almost instantly in the other software. To its credit, I don't think there's any effect or feature in C1 or LR that couldn't be achieved in DR, but it would usually be a lot more work.

Another problem I had was that RAW support seems to lag behind C1 and LR quite a bit, especially for cameras with new or unique sensors. I have a FujiFilm with an XTrans sensor, and it took a long time for it to be supported in darktable. On a similar note, it is pretty far behind on things like lens correction.

Overall I just get stuff done faster and easier in C1.

Not yet, I did some cursory glances and it looks like they're missing RAW support for quite a few camera(all the Sony A7* series). They also seem to have very limited lens correction profiles(missing some classics like Canon's 35mm F1.4).

I will say their UI and look & feel looks very much like lightroom although I'd be curious what their culling workflow is like.

I have tried it many times, I wanted to switch several times to Linux, I even bought a laptop suitable for Linux, but shortly after got a macbook.

I find that Darktable is in no way a good competitor for Lightroom. The image processing quality seems to lack, speed lacks, file support is not always good. It looks like a nice clone, but apart from the looks it has to work well.