I have been using bibble for about a year now. Its the best photo editing software that ran on linux that I could find. It probably isn’t as polished as Photoshop but it has its own great features like threading so it can use all of your cores for rendering.
Just over a week ago I noticed it had been bought by Corel and its been re-branded to AfterShotPro. I really hope they continue to develop it and provide Linux support.