of couse we're back at gui, because gui is what the user interacts with, and as +Jake Russo
already explained very well the linux UX as it stands will never be ready for general public, that's why I couldn't market a linux desktop to the general public, that's why linux desktop is stuck at such a low market margin.
About the rest of your comment, of course gimp works fine in kde but again it doesn't fit in with other kde applications or the kde desktop because it uses a different toolkit and as consequence different interface design. About qbittorrent, try using it in gnome 3, sadly, gtgtk only works with gtk2, not 3. And for vlc I have no clue how it looks under osx but take a look at the windows version which fits right in. This is not fault of the applications but the toolkit they use. As there are no common environment, every toolkit uses whatever they feel like which leads to no visual consistency between them despite efforts of some distros to create unified themes. And to give you an example of integration, let's say I use kde and I configure it to have the application menu on the top bar, every other application not native will not behave like this, just like x11 apps on os x.
As for the video editors comment, if it's feature incomplete it's effectively useless for me
, and any other person that relies on missing features, that's a fact, so reducing everything to the lowest common denominator and saying there are x amount of software that is capable of the most basic functionality (cutting and joining video in this case) is not very accurate as there's a whole lot more to video editing.
And finally, about the software available, for everyday use it is there and I use it, but it's not nowhere close to the polished experience that should be for all the reasons stated above. I use gnome 3 and for consistency sake I've stuck myself using whatever fits best, like polari for irc despite being extremely barebones, geary for email which fits better then gnome's own evolution and corebird for twitter even though there are other applications more feature complete.