Well... nobody is perfect and Gnome guys have lots of room for improvement too.
But again... Quality of your UI software isn't everything. Sometimes a game-changing feature appears out of nowhere. Apple's multi-touch has changed how I use computer dramatically. And it has almost nothing to do with the software itself: it's a driver+hardware combination that I personally find impossible to live without. OSX allows me to do a lot with just one hand, so I can hold a cup of coffee in another: flip pages, zoom in/out, scroll up/down, etc. This was enough for me to stick to OSX for my daily non-programming computing needs. I even started reading books in PDF format, something I previously could believe I could do.
Yeh - killer features are a big bonus. Thing is they are cool to work on - and so quite a few seem to work appear, pulling people in. With OSX and Windows that's fine because IMO they have that extra level of ease and Usability that a consumer OS needs. Linux doesn't have that left - I bet a lot of people drawn in with a gimmick are left struggling with it after a few weeks...
I still maintain that Linux is lacking a simple UI to pull it into the mainstream (ALL Linux not just Ubuntu).
But I think Ubuntu (and other distro) teams haven't made use of the Window managers well at all. Menu's, applications and other bits and pieces are just too confusing for the average Joe user.
UI extends even beyond the windows themselves.
As someone commented I think Linux devs are waking up to how important UI and user interaction is. But
- It's a mess, and a hell of a job to fix
- No one with the proper expertise is involved in the projects
- It's not a glamorous thing to be doing (compare to "cutting edge" stuff
- There seems to be this ingrained anti-M$ vibe that means no one can take influence from them. ?? UI is one thing M$ tend to do really well in Windows. They spend a LOT of money researching it.....