"Coherent" is not a word often used to describe the Linux Desktop experience. How many different ways do I have to copy and paste again? Which ones are valid in which contexts?
The OS is coherent (arguably more so than most) even if the GUIs aren't necisarily. A big part of that is because most of the useful apps are shell/VTE apps. Even still it's not like other OS vendors are much better at building good UIs: How many frameworks has MS gone through just to say "screw it, write web apps?" Even Apple can't get everyone onboard with Cocoa.
Wouldn't this be more applicable to BSDs more so than Linux? One is a kernel and userland made by the same team and packaged together and the other is a kernel with a bunch of different philosophies packaged around it.
I don't want to be pedantic and write "GNU/Linux distributions" every time. People know what you mean when you write "Linux." And the result of the distribution model is something similar to the BSDs (when you pull the projects apart I'd argue they're really not so different socially.)
