I just purchased Devonsphere express which I am thoroughly enjoying. I am not so much enjoying the blurry pixelatedness of a non-retina app on a retina display! I know its a big job to re-do an entire UI with 2x graphics, but I’m hopeful it is in the pipeline! At least a retina version of the menu bar icon. 
It won’t be part of the upcoming minor maintenance releases but it’s definitely planned for future revisions.
Great to hear!