My problems with Gnome 3:
-Extensions are a very awkward approach to what should be simple config changes. For example, there are two hotcorners by default, upper-left and lower-right. Rather than offering a straightforward configuration to disable it, you have to dig through extensions and find either the extension to disable upper-left, the different one to do lower-right, or the third one that disables both. This accumulates quite atrociously with all the settings.
-Because of the extensions being particularly invasive and pretty much required, the 'oh no' screen is easy to hit.
-In the event of an 'oh no' screen, gnome shell does not care that your apps are still running and could conceivably be used if gnome-shell would just let you restart without logout. It just says 'screw you, log out and kill all your applications'. I've tried starting metacity and it will run, but I can't get rid of the 'on-top' oh no screen.
-No window title search, like has been in Compiz scale and KDE for a very long time. Very hostile to large window count scenarios.
-No way to show all windows belonging to an application in activities view exclusive of other windows
-The application button is sloppy-focus unfriendly

What I like about gnome 3:
-Hot-plugged multi-display is handled pretty well (one of my biggest reasons to lean toward gnome away from KDE, less work when I dock my laptop).
-I actually do like the new alt-tab,alt-above-tab. Having two tiers helps that be almost useful (had given up on alt-tab as unscalable without this)
-Nominally having all task switching/launch elements hidden, but taking over the full screen when you want to switch or launch applications. Keeps my workspace cleaner and doesn't limit the real estate used to facilitate task switching/launching to some small corner of the screen when it is the only thing I am thinking about while that is happening.

How is VLC supposed to play videos over KIO slaves when VLC is a pure Qt application that does not support KIO?