I've been spending my evenings churning through heroics on the Cataclysm beta. It's a bit unsettling to heal as a holy paladin in the dungeon environment, because it feels like you're playing bizzaro-WoW. Holy Shock is your main heal, Holy Light isn't the button you go to when your tank is dipping dangerously low, and you're actually watching for procs instead of settling into a steady state of heal spamming.
Not only that, but we've now got options when it comes to healing more than one target. Our precious Glyph of Holy Light is gone, but it's been replaced by far more powerful options. Holy Radiance allows us to heal either melee or ranged players, based on our location. Light of Dawn gives us our AoE toolbox a ranged option, with a sweet graphic effect to boot. The core fundamentals of paladin healers are still around, and our Hand spells are still as potent as ever, but now we've got a more robust set of tools to handle every situation. Needless to say, your number of keybindings will expand significantly.