Pasting paths into Nautilus' "address" bar
You can activate the "location" view with CTRL+L. To permanently show the path instead of "breadcrumbs" you will have to manually change a dconf key:
gsettings set org.gnome.nautilus.preferences always-use-location-entry true
To revert the changes simply execute the following command:
gsettings set org.gnome.nautilus.preferences always-use-location-entry false
Copying file paths in the Save/Open dialog with Nautilus 3.4.2
As @AliNa pointed out, it used to be that you could access the location of a file or folder in the save/open dialog in the same manner as you can in a regular Nautilus window
This feature has been abolished in recent Nautilus releases as part of GNOME's design philosophy.
However, you can still access the file and directory paths from the context menu:
It seems as though this method has been removed as well in more recent revisions of Nautilus (the ones that ship with Ubuntu >12.10)...
How to copy the current path from Nautilus?
Typing location path instead of clicking directory buttons in the file picker dialog?
How do I change dconf keys without a gui (for a post-install script)?