There are many other smaller user-visible features. A rapid-fire list of some of those features is below.
It is now possible to run the GIMP in batch mode without an X server.
We have a GIMP binary (GIMP-console) which is not linked to GTK+ at all.
Improved interface for extended input devices
Editable toolbox: You can now decide which tools should be shown in the Toolbox, and their order. In particular, you can add any or all of the Color Tools to the Toolbox if you wish to.
Histogram overlays R, G and B histograms on the Value histogram, and calculates the histogram only for the contents of the selection.
Shortcuts are now shared across all GIMP windows.