I was on a trip recently and forced myself to do all my image processing with Darktable, and have come away feeling much better about the UI than I started. A few things that have helped me make the transition:-
- Adjusting the UI element colours to be a bit less contrasty made it easier on the eyes - read Elle Stone's review at http://ninedegreesbelow.com/photography ... useability for details on how to do this.
- Learning the hotkeys - F1-F5 for colour labels, 1-5 for rating, F11 for fullscreen, hold down Tab to just show the image and lose all the interface elements. Others were also useful, but just getting that set in my head reduced my irritation levels considerably.
- Figuring out that you can move the sliders quite finely by hovering over them and using the mouse wheel, which meant I was much less frustrated by fine clicking around
- Using the right click to get at the Bauhaus widgets for exposure/black levels etc, which actually makes fine tuning very easy.
- Watching pretty much all Robert Hutton's videos - https://www.youtube.com/playlist?list=P ... o1B468zEA0. They were a big help.
With this, I got in the habit of culling images by hovering over them with the mouse and labeling/rating using the hotkeys in the lighttable, then just selecting all images of a particular colour label for further editing in the collect module. Then flip into darkroom mode, and edit each image in turn, moving between them with space/backspace. It drives me mad that the cursor keys don't work, but still.... I expected to get annoyed enough to switch back to ASP, but actually didn't fire it up for the whole trip, in the end.
There's still much about the interface I dislike - the tagging features and library management aren't great, and I think it's pretty much unusable on a laptop without an actual mouse, but I got some pretty good results. I like the mask manager - that's better than Bibble/ASP, and doesn't have the single heal/clone layer limitation. Once you figure your normal workflow out you can stick those modules to your favourites list. Also, the graduated density filters and masks make it easy to selectively adjust different areas of an image. I went into that trip with the same "terrible UI" view as you, and have come away with a view that the UI is still flawed and incomplete, but is manageable. The image quality is better than ASP ever managed as well, IMHO.
Give it a try for some serious work, and I'd be interested to see what you think. The linux options aren't many - I didn't want to run anything through emulation layers or VMs, so it's Darktable, Lightzone, Photivo or Rawtherapee. Darktable is open source, has active development and an interested community, and Linux is the primary platform, so I think that the time I spend there isn't wasted. I'm tempted to try to add better tagging support to it, but we'll have to see how time goes.