There is something I really miss in GIMP, but you can very rarely find any other program that supports that, not only when it comes to raster image editing. Remember all those situations where you edit an image, then undo a lot of times to see how it looked before, and now want to change something different. If you do so, all changes are lost, it’s like cutting a branch from the tree.
What I’d love to see would be something like an undo/redo tree. I missed that for a long time, but the idea came up again when I recently saw this image on the GIMP UI Brainstorm, by Jan Rüegg:
It shows pretty clearly what it wants to say. Perhaps the options in the context menu would be really difficult to implement, like moving a branch, or a “leaf”, but the general idea would be worth the effort.
I know that GIMP isn’t meant as a replacement to Photoshop, but as Photoshop doesn’t have this function either, this would be a clear advantage over that software. I’m sure many people would switch, or at least start using GIMP.
When I asked that on IRC, it started a big discussion, luckily not about if it’s useable, but rather if/how it would be doable. It would make sense as a first step, as a pre-undo-tree, to implement saving history to the XCF file, but considering where GIMP is heading, it could be considered useless. GIMP tries to become a non-destructive editor. (Although it would be still cool to see your steps one by one.)
Nevertheless, for actions like drawing, selecting, filters and so on, it would be cool to have something similar to a undo-redo-tree. Sure you can argue now, if that won’t be going to be wasted development time of code what will be thrown away later, but it really depends on what GIMP wants to become. We’ll probably have to wait. And hey, why not become versatile?