They got bashed for removal of options (that could be hidden from average user), also they changed a lot of things and more or less reimplemented things that they didn't want to do at the beginning (and where bashed for lack of), so I'd say they made a lot of mistakes - for me gnome is usable without heavy tweaking since last year.

Which means it took 4 years to get it to usable state where i don't have to download tons of plugins to make it effective environment for work and multitasking.