Totem's fullscreen controls don't work with many touchpads, this bug has been around since totem 3.0. I've seen this happen on 3 separate laptops from 3 different manufacturers. You'd think a basic feature on the *default* video player wouldn't be broken for so long.
Since gnome 3.6 brasero is completely unable to add mp3's to an audio cd. Bug reported ages ago but no activity on the bug report (and is generally a buggy mess anyway)
GDM 3.6 is just super buggy in general. it loves to often hang on logout for example
The new lock screen is ridiculously buggy, it will randomly start acting very "slow" (you hit "lock screen" and then it locks like a full minute later. Sometimes it also takes forever to unlock too.
They break/change screensaver inhibiting with almost every fucking release, so media player's have to play catch-up
the "lock screen after" option appears to be completely broken in gnome 3.6
gnome-shell still tends to randomly hang on login sometimes, I've seen this on a variety of hardware. doesn't happen often, but real annoying when it does
Gnome-shell 3.6 has a massive memory leak, everytime you click an item on the top panel memory usage rises and never gets released
tracker crashes *all *the*time.
Empathy/telepathy is just a horrific, buggy mess. still is and always has been. First thing I have to do on any install is install pidgin
I like both gnome-shell and unity as interfaces, but they are both way too buggy and need to step up QA.