Despite any arguments to the contrary, I don't feel that spirit is a true secondary stat. I know you can reforge in and out of it and that it's not as ubiquitous as intellect, but it's actually closer to being our fifth primary stat. In Mists of Pandaria, intellect will no longer grant additional mana, making spirit the only game in town for improving longevity. Because of the way holy paladins function with the new Judgements of the Pure regeneration mechanic, spirit has gone from a good choice to a must-have stat.
When we start talking about the true secondary stats, we realize that there's a lot of baggage here. Haste rating was the de facto champion due to its ability to affect all of our heals, critical strike rating was avoided after the removal of Illumination, and our master rating has gone through more iterations than any other spell in Cataclysm.