There's always a hypervocal minority in any a GNOME related thread claiming that GNOME 3 was a regression, it has too much padding, it's too slow, it takes too much memory, it doesn't allow you to configure something, etc etc etc.
Meanwhile, every big distro chooses it and millions get on with it just fine.
The button layout in GTK dialogs makes essentially no sense from a UX perspective, because, yes, people read things left-to-right (in LTR languages), top-to-bottom, and the program flow should reflect that. Apart from that problem, buttons on top makes little sense for other dialogs due to the awkward mouse movements it forces. Mouse moves down, selects a file, maybe picks the file type (do I want a jay-peg or a jif?) and then... has to move all the way up again?
I'm mostly not in a direct line-of-fire for user complains due to Gtk/Gnome (but actually received some, mainly around, you guessed it, file dialogs), but the impact zone is basically next door. And it's not exactly happy noises and good smells coming out that door. This is from users who couldn't care less what the thingamajing is called and don't know or care if their Linux explorer is called Dolphin or Thunar. What they do notice is that they've got an OS upgrade from IT and now they're angry because two thirds of the UI are gone and the remainder makes less sense to them.
