Windows 8 has very specific desktop improvements, like:
-More shotcut keys;
-Better useability (tiling in multi-monitor setups, non-transparent theme, more space for icons in the taskbar, single point of all settings, better file-transfer dialog);
-Userspace file system (useless for Metro).
Apple flattened iMacs, came out with ultrabooks and high resolution displays, duplicated iOS advancements, better cloud integration and better backup.
Afterthought my ass.
You can like Gnome shell all you want. No one says that Gnome Shell isn't a nice GUI for its intended audience. We are simply arguing about its suitability as a workstation GUI. Fedora is not a tablet distro and is definitely NOT a casual desktop usage distro: It is a distro targeted at Power-Users and above and a testbed for Red Hat so its focus should be in productivity, not tablet and all-i-do-is-facebook-and-media kind of usage...
As for Gnome 3 extensions, don't make us laugh, seriously... Most of them are useless and broken. And there are not many to begin with...