for starters, toolbox grouping and icon theme changes are reversible in settings, and in fact the "legacy" icons have gotten a lot of love in 3.0. they look nice at high dpi now! (it's a shame we moved away from the tango aesthetic in linux land too early because god the style can look so right and crisp on hires screens)

having used all the 3.0 RCs up till now, i can assure you all gtk3 has done is made life nicer on all major platforms. for gimp's faults (now markedly fewer) it's an image editor, a thing with a distinct purpose and pretty immediate feedback on indulgent changes nuking productivity. the cancerous low-information-density, look-over-feel trends that we associate with new gtk versions by way of gnome's visionless bikeshedding blessedly does not translate to this new gimp. pinky promise. go use it. you'll like it.