None of the other solutions worked for me in Gnome 3.14 on Gnome Ubuntu 14.10. What finally worked was creating .desktop files by hand.
First, make the folder
~/.config/autostart/ if it doesnt exist.
Then create a
~/.config/autostart/my-app-to-startup.desktop file for each program you want to start on login.
For example, here's what my
~/.config/autostart/pidgin.desktop file looks like:
Comment=instant messenging client
Here is the specification for the keys you can place in those .desktop files. This puts some context to that specification as to how it applies to startup applications as well as some exceptions to those rules. Credit for this solution goes to this Linux and Friends site.