The 3D CAD software CATIA has a very good UI. It has themes for Windows and Unix. I would say all other 3D programs have a better UI than Blender (even 2.6, though it was a lot worse pre 2.6). Blender just doesn't adhere to common conventions and is inconsitent, has little tooltips, and some function only accessable via shortcuts. Gimp had similar UI problems in old versions - it could be a lot more popular, but Photoshop's UI simply sucks a lot less.

Common UI conventions are for common apps. Blender for example is built with mousing in mind, and so hovering in whatever panel makes that panel active. So the commands are for the context of that panel. You say little tooltips but you can hover everywhere and get loads and loads of tooltips. Granted many need improvement but to someone reading you, they'd think it doesn't even have tooltips, which is not true, it has many many tooltips.

CATIA? So I looked at CATIA and a cursory glance shows that they aren't all that conventional either. One shot I saw was of v5 with a bunch of tiny floating undockable overlay windows. Yeah great UI. The catia sketch tool seems awesome, but that seems to be a smaller subset of the software for prototyping stages. I realize maybe it's unfair to ask, but is there an ultimate video walk through that you think showcases the great UI of CATIA? Does CATIA also have all the features and expectations that blender has? Such as animation, advanced texturing, lighting features. It certainly seems to be a capable modeler based on some final render images I've seen and it probably allows for physic simulations I'd gather

CATIA v5/v6 has toolbars on 3 sides of the screen. Every toolbar part can be activated and moved around, snapped-in, etc like in common UIs. There are no floating windows that stay there or are there by default. But there are dialogs that open to set specific settings, dialogs are a common UI pattern as well. In v6 some of the dialogs have been replaced (made obsolete) because of the 3D editing mode. In comparision, the Blender UI doesn't follow common UI patterns at all.

You can do everything you can do in Blender also in CATIA (except fluid physics, game engine) but you can do advanced simulation like finite elemente physics and electronics. Also CATIA is a CAD software, so there are of course differences and it will usually take longer to create a 3D model, but afterwards it can be built in real world with real world physics.