Now, I know this is completely subjective, so please don’t flame me. I’ve never been entirely satisfied with linux whenever I decided to install a distro like Ubuntu, Fedora etc. because of their awkward positioning and spacing of widgets.
Have a look at this:
Notice the awkward spacing of the text field’s text.
I’ve seen many Gnome themes that look good on the surface but it all somehow breaks down, awkward spacings, strange borders. Etc.
The entire linux desktop doesn’t have the visual integrity of OSX for instance, and I wonder why. If there is any example of a nice integrated Linux environment, please please please show me, I really WANT to use Linux.
(and I know, there’s QT, and other managers like KDE etc. I noticed the same thing, so it probably isn’t GTK or Gnome alone)
You basically just answered your own question – Mac OS X has one desktop environment (centered around Cocoa), which has a lot of very good programmers and designers spending much time designing, discussing and implementing it.
With "Linux", there’s not only different window managers (Gnome, KDE, Flux/OpenBox, Enlightenment, etc etc), there’s different UI toolkits (QT, GTK+, Tk, wx, etc etc), different versions (in common use), and countless different ways of using/implementing them.. Compare List of (mainly) Linux GUI toolkits compared to for Macintosh (all of those, bar Cocoa, are for old Mac OS versions).
There’s many good designers and programmers working on GUI toolkits, but they are spread over so many different projects. Even if they somehow were put onto a single project (Say, "wxQtGnome"), there would still be countless applications that use a different framework, or even a different version of one.. Then you still have the problem with inconsistency. Again, compared to Mac OS X, where if you have a GUI application, chances are it will be using Cocoa (which has a decent UI creation tool, which helps developers layout applications according to Apples Human UI Guidelines)..
As for a nice, integrated linux desktop environment – I would say the default Ubuntu installation is probably the closest to this. A decent theme, and all the applications fit fairly well together.