I use the GIMP almost every day when making graphics on Linux, and I’ve been doing so for a long time.

Of the top of my head, here is a list of things I wish the GIMP had:

# *Layer grouping*

# *Recovery of unsaved and recently-not-saved files*; there is a temporary swap space, and GIMP should be able to retrieve files from it

# *16-bit/channel support*

# *Easy record & playback actions*

# Refinement of some of the dialogs to save space

# Along with the previous point, possibly a small version of most widgets (small scrollbar, small sliders, etc.), also to save space

# Less default filters & add-on filterpacks (there are so many filters by default, and I only use a small handfull, so it’s sometimes hard to find some)

# Combine some of the filters in a filter browser preview thing, or at least have a consistant preview among filters

# Proper packing of dialogs (resizing totally breaks on most filters, usually in the preview window, but also in other places)

# Layer “comps” (Photoshop added this a couple versions back, iirc — it’s a saved state of layer status including visibility, opacity, and layer mode)

# The ability to save workspaces, as I hate accidently closing my custom layers dialog window group and losing the layout and custom dialog tabs I tossed in there

# Versioning of files would be nice, could possibly be handled outside of the GIMP too

# Compression of XCF files by default, instead of having to do filename.xcf.gz (which, thankfully, *is* handled in the GIMP transparently)

I’m sure there are many more things that could be listed, but these are the features I can think of right off the top of my head.

By-the-way, It has nearly been a decade of the GIMP! Hooray! (: