I’ve been using this editor for a while, in addition to Digikam and Ufraw. I liked Photivo a lot, but as with all the other programs I tried, it just didn’t quite fit into my current workflow. It was too complicated for the bulk of my editing. The few things I can’t do well in Digikam or Ufraw, I can do especially easy in Darktable. A good example is removing dust spots in photos. I’ve tried using the remove artifact option in Digikam, but it’s kind of hit and miss as far as results, and overall I just don’t like the way it works. There is a spot removal option in Darktable and it works incredibly well.
Another thing I like about Darktable, it does fit well into my workflow. Normally I convert from RAW to PNG in Ufraw, applying curves, adjusting exposure, white balance, etc., as necessary. I then resize/crop, sharpen, and tag the photo in Digikam and save it as a jpeg. If there’s something I can’t do well in Digikam like spot removal, I insert Darktable into the middle of this workflow, editing the png from Ufraw, and outputting the edited version as another png, so I have no loss in quality in that intermediate step. That’s where I often have a problem with other editors, either I can’t edit a png, I can’t retain exif data in a png, or I can’t output as a png when I’m done.
Digikam is the mainstay of my workflow, since besides editing, it’s also the organizer for my thousands of photos, with a great database backend. Ufraw has been my mainstay for raw conversion, as I’ve never liked the raw conversion in Digikam, and I’ve never found anything that converts better than Ufraw. I still have to experiment more with Darktable to see how the raw conversion compares to Ufraw.