oQueue allows you to make groups for many things that Other Raids don't.

Examples?
1 - Older Expansion Raids. Other Raids allow you to browse for but don't allow you to list your name for, so it simple don't work for Older Xpac Raids.

2 - PVP! BG Premades, Arena/RBGs, World PvP.

There are more advantages, but that two are already enough for me. It's not perfect, but it's the best addon for these purposes for now. :)