Kurn has a very good roundup posted. I'll just focus on a couple of the major changes for Holy Paladins.
Holy Radiance has changed significantly. It's now more of a heal you cast multiple times on the raid, rather than a "fire-and-forget" heal. The new Holy Radiance is a group heal with a direct heal component and short heal-over-time component. It also generates one Holy Power with the Tower of Radiance talent.
The heal-over-time component means that you should cast Holy Radiance on different people if you cast it multiple times in a row. Cast it on Player 1, then Player 2, then Player 3, then back to Player 1 to get the most healing out of it.
The thing is that Holy Radiance is no longer something you have active while you are tank healing. Rather, you have to switch modes when you use it, to move from tank healing to raid healing. A lot of times, this will be the wrong thing to do, as your raid will rely on you to keep single-target heals flowing on the tanks while other healers raid heal.
But now, you might be assigned to raid heal, while someone else tank heals, and that's when you bust out Holy Radiance.
In raid-healing mode, the new rotation is something like:
- 3x Holy Radiance, 1x Light of Dawn - Maximum throughput, high mana cost
- 2x Holy Radiance, 1x Holy Shock, 1x Light of Dawn - Less throughput, but less mana cost
You'll have to see which works out best. But the key is to remember to target different people when you cast it in succession.
The other major change is to Judgement. Along with the Haste buff of Judgements of the Pure, you also get a significant boost to your regeneration from Spirit. This means that you must Judge as soon as you enter combat, to get the JotP buff up right away.
You don't need to judge on cooldown any more. In fact, it is a waste of mana to do so. So you may want to move your Judgement keybind if you are in the habit of hitting Judgement often. But you absolutely cannot let the JotP buff fall off. I would recommend judging every 45 seconds or so.
Get the Judgements of the Pure buff up ASAP, but only Judge to refresh the buff, instead of Judging on cooldown.
Stat Value Changes
Gear-wise, the Judgement change means that non-Spirit builds are no longer viable. Spirit is pretty much established as the best secondary stat. (Intellect, of course, is still the best overall stat.)
There is some debate over whether Mastery or Haste is the next best secondary stat after Spirit. At this point, I would lean towards Haste, but I think it's still inconclusive.