There's a lot of duplication (Colors, Tools>Color Tools; Brush in Toolbox & as Dockable window), things that are out of place (View>Show Grid, Image>Configure Grid), common workflows that require more clicks than in other editors (Select-Copy-DeSelect-Paste), odd choice of defaults (When resizing canvas, choose "resize all layers" instead of "None"), and other odd design choices (Toolbox can't be a dockable window, Toolbox needs scrollbar if vertical Resolution<1024) that make GIMP occasionally frustrating to use, despite being an otherwise awesome tool.