Except that GIMP's multi-window implementation is as shitty as possible, especially if you use focus-follows-mouse. The palettes all freak out and forget state

Except that GIMP's multi-window implementation is as shitty as possible, especially if you use focus-follows-mouse. The palettes all freak out and forget state in a most unusable way as you move the mouse over to them! It doesn't help that they're implemented as normal windows so they constantly get buried, lost, closed, and forgotten. Besides, you really want to mouse across monitors to use the basic UI?