Many GUI elements do not scale. For example apps like Chrome and Skype render very small, almost unusable. I'm guessing these apps are not going through X to render. Others like Firefox render ok, but the icons are a bit on the small side. Even Gnome 3 itself doesn't do a great job, when you are in the Workspaces view the taskbar on the left is a bit small. The Settings/Sound menu in the top right doesn't correctly guess how much horizontal space it has and renders narrowly. Many Gnome apps, like the Settings app, renders a bit small.

I might try and install Mate and see if it is any better. I have no interest in using Unity or XFCE so I can't comment on those.