There's been some cleanup of the UI, our Auras are gone, and the Seals now appear in their place. Hand of Reckoning has finally been stripped of the "Hand of" part, and is just named Reckoning. It only took three years.
I only got to look at Holy and Retribution, because changing specializations is broken.
For Holy, single-target healing is more or less the same as the previous edition. The only significant difference I saw was that Cleanse now has an 8s cooldown, but dispels all relevant debuffs.
AoE-healing seems to have a lot of tweaks, but I don't think it has fundamentally changed. It still follows a Holy Radiance-Holy Shock-Light of Dawn pattern, but there are little changes. Holy Radiance currently heals the target and then does 50% of the heal to surrounding players. A bit of the healing also transfers back to the Beacon of Light target. It also causes Holy Shock to behave much the same way. Light of Dawn may no longer be a directed cone, but that might be a bug.
For Retribution, it feels much the same as previous, i.e. all the same abilities. But the Holy Power cycle has been sped up. Basically all non-finishers now produce Holy Power, so you can use Templar's Verdict essentially once every 4 GCDs. The finishers also cost exactly 3 holy power, simplifying things a little bit. I generally liked the feel of Retribution, though many posters on the forums are saying that it feels too slow. Personally, I don't see their argument, it felt like I almost always had a button to press. But I don't play Retribution a lot and am not an expert.
Retribution also got a full-blown AoE rotation, with where you can use Seal of Righteousness instead of Seal of Truth, Hammer of the Righteous instead of Crusader Strike, and Divine Storm instead of Templar's Verdict.
Hopefully I will be able to take a look at Protection in the next build.
So far, it feels like paladin specs have been cleaned up a fair bit, but no fundamental changes to the way we play. Which I think is pretty good. I thought paladins played fairly well in Cataclysm and am happy to see that continuing on into Pandaria.