Hi Thibaud,
Thanks for that Nuke link. I'll check it out.
I like Modo OK (a little too "modal" for me, though), but prefer Rhino and its cousin
MOI for 3-D modeling. You should get the MOI demo. IMO it represents the future of 3-D UIs. The guy behind MOI (Michael Gibson, the original Rhino developer) is a programming genius with a good hand wielding Occam's Razor.
The ultimate UI for a graphics application for me is Corel PSP XII. You can essentially have any form of interface you want: tab documents or MDI, floating or docked toolbars and palettes, combined or separate tool panels... essentially anything. I absolutely love it and want that interface in all my tools of that ilk.
A mix and match combination of UI features from Adobe Lightroom, Paint Shop Pro, Picasa, and XnView would send me into interface heaven. I'd have to change my pants.
Intimidating to contemplate the programming effort that would require, though.