GNOME3 has actually become quite usable, but I was really annoiyed by the inability to disable actions on "critical low battery" (Additionally, there is no way to define what "critical low battery" is and with a big battery I assume this might well mean that you cannot use the machine anymore even though there is half an hour of juice left). Add to that bnc#738782 which leaves my screen unlocked after suspend and I decided it was time to use someting sane -- like xfce4-power-manager -- instead.
However, it's not that easy, as everything power related is hard-coded into the gnome-settings-daemon -- and even in different places.
So here is a package with a patch that simply disables the handling of all the power-related keys in the media-keys (!) plugin and additionally prevents the build of the power plugin completely.
Now just start xfce4-power-manager (and maybe use the Evil Status Icon Forever shell extension to make it show up in a visible place).
The patch is here, it is clearly not upstreamable but I'd rather have an ugly hack than an unusable "good solution" :-)