Steps to reproduce:
1. Disable power saving
2. (Re-)boot (logoff may suffice, though I’ve not tested this)
3. Login and don’t touch mouse or keyboard after that
4. Wait

What happens:
Within half an hour (on my system at least) the display signal is turned off (monitor reports ”No signal”).

What you expect to happen:
The screen to stay on as indicated by power saving settings.

Additional info:
1. Any keyboard or mouse activity seems to make it obey the setting: after that the screen won’t go blank on its own (irregardless of whether or not the bug has manifested itself during the session).
2. I’ve disabled screensaver as well, though that probably doesn’t concern this bug.
3. From bug #854624’s comments I picked up this settings listing command, in case it helps:

jani@saegusa:~$ for c in `dconf list /org/gnome/settings-daemon/plugins/power/`; do echo -n ”/org/gnome/settings-daemon/plugins/power/${c}=”; dconf read /org/gnome/settings-daemon/plugins/power/${c}; done
/org/gnome/settings-daemon/plugins/power/sleep-display-ac=0
/org/gnome/settings-daemon/plugins/power/sleep-display-battery=0