I would seriously tackle these things about GNOME, given the chance:
- Add a 'reveal in file browser' command to Rhythmbox's context menu,
- Make the filename display in Rhythmbox and any program that gets it so horribly wrong into one box rather than two, one for folder and one for name,
- Make the mouse-during-alt-tab work à la MacOS,
- Make Epiphany block per-window, not the whole process when a dialog pops up.
- Make process startup times as low as possible, by delaying initialization as much as possible, and eliminating as much as I can.