I'd like to reflect on the holy paladin healing I managed to do in beta. I didn't do raids there, but I did do a decent amount of dungeons and I've seen most of the raid boss videos. At first I pugged a couple of normal modes in full blue heroic gear and the damage/health ratios feel... scary at first. That's the only word I can use to explain it. You will struggle with normal modes, especially if you haven't seen them yet. Our heals at 85 literally do the same amount of healing that they do at 80. The only thing really boosting their effectiveness is spellpower itself, not new ranks or anything like that. Everyone has a lot of health, floating around 60-90k I believe. Damage has scaled up, especially AOE damage. Most of the time during a fight people are at deficit health. In starter gear this will be even more true. Holy radiance is a key spell in our new arsenal. It will save your group. A lot. Don't be afraid to use it.
Later on I did some heroics in the fully epic premades for the heck of it to see how gear scales. Heroics are still decently challenging in full epic raid gear which is refreshing. With full heroic blue gear heroics are challenging. With starter 85 gear they will be quite brutal. With full epics I was able to compensate for mistakes my group made and recover after situations that I wouldn't be able to handle in early blues. I simply would have run out of mana in that other gear. This is as it should be.
Mana is back. Even at 80 with 4.0.3 mana isn't an issue. We can use spells like Flash of Light over and over again, albeit we do see mana dip if we use Flash a lot at 80. At 85 you'll have to change. You will switch from using Flash of Light because even using 3-5 of them in a fight will sap your mana pool. HS+HL+WoG/LoD and Holy Radiance will be your best friends and FoL/DL will be second class in your toolbox. Divine Sacrifice will be your best friend for saving damage on the tank and transferring it to the free healing on yourself. Cooldowns will be your best friend again (AW+Divine Favor are incredible at getting a group back on its feet with Holy Radiance). Divine Light will be a strict backup spell, and now that Infusion of Light works to speed it up it's a great spell to heal someone from a very bad deficit. It still costs an arm and a leg though.
You'll have to take my word for it that 80 healing, even with 4.0.3, is nothing like Cataclysm. It's just a totally different environment due to health pools, spell cost, spell potency, and encounters in general.