Intellect has been our best stat for quite some time, and Cataclysm has only reinforced that. We get spellpower, mana, and critical strike chance from every point of intellect, which makes it valuable for every aspect of holy paladin play. We want to gem for intellect, enchant for intellect, use intellect consumables like Severed Sagefish Head and the Flask of the Draconic Mind. All of our spells scale off of spellpower, which makes it an amazing throughput stat. The fact that it gives us critical strike rating is just icing on the cake.
Divine Plea's mana regeneration scales off of our maximum mana, and so stacking intellect gives us both mana at the start of the fight and then additional mana every time we use Divine Plea. My only advice is to be sure to use all plate gear, as we receive a 5% intellect bonus when wearing all plate. Mail caster gear may seem attractive, but the intellect loss isn't worth it. Intellect is designed to be our best stat, and that's why we can find it on all of our gear. Even if you hated intellect, you can't get rid of it. The real gearing decisions come down to choices between the secondary stats.