New Priest Spells
Heal (available at level 16): While priests already have a spell called Heal, the existing version becomes obsolete at higher levels, which is something we intend to change in Cataclysm. Introduced at a low level, the "new" Heal spell will functionally work much like a down-ranked Greater Heal did in the past, adding more granularity to your direct-healing arsenal. If you need to heal someone a moderate amount and efficiency is an issue (making Flash Heal the incorrect spell for the job), then Heal is what you want to use. Heal is intended to be the priest's go-to direct-healing spell unless they need something bigger (Greater Heal) or faster (Flash Heal). We will be following a similar philosophy with all the healing classes.
Mind Spike (level 81): Deals Shadowfrost damage and puts a debuff on the target that improves subsequent Mind Spike damage. The intent of Mind Spike is to fill a niche missing in Shadow DPS, though it may be occasionally useful for healers as well. Mind Spike provides a quick nuke to use in situations where the priest doesn't have time to set up the normal rotation, such as when adds are dying too fast or you have to swap targets a lot. Spamming Mind Spike will do about as much damage as casting Mind Flay on a target afflicted with Shadow Word: Pain. The idea behind the debuff is that when you cast Mind Spike, we expect you to cast a lot of them; we don't intend you to fit it into an already full Shadow rotation. It also provides Shadow with a spell to cast when locked out of the Shadow school. (School lockouts will no longer affect both schools for multi-school spells.) 1.5-second cast. 30-yard range. No cooldown.
Inner Will (level 83): Increases movement speed by 12% and reduces the mana cost of instant-cast spells by 10%. This buff will be exclusive with Inner Fire, meaning you can't have both up at once. Inner Fire provides a spell power and Armor buff; Inner Will should be useful on a more situational basis.
Leap of Faith (level 85): Pull a party or raid member to your location. Leap of Faith (or "Life Grip") is intended to give priests a tool to help rescue fellow players who have pulled aggro, are being focused on in PvP, or just can't seem to get out of the fire in time. Instant. 30-yard range. 45-second cooldown.

Changes to Abilities and Mechanics
In addition to introducing new spells, we're planning to make changes to some of the other abilities and mechanics you're familiar with. This list and the summary of talent changes below it are by no means comprehensive, but they should give you a good sense of what we intend for each spec.

 * All HoTs and DoTs will benefit from Haste and Crit innately. Hasted HoTs and DoTs will not have a shorter duration, just a shorter period in between ticks (meaning they will gain extra ticks to fill in the duration as appropriate).
 * We want to bring back Shadow Word: Death as an "execute" -- something you do when the target is at 25% health.
 * While we want to keep the priest's role as a well-rounded healer, we also want to make sure the class is a viable tank healer, which is something priests moved away from a little in Wrath of the Lich King. Greater Heal will probably be the tank-healing spell of choice, though we've also discussed giving Discipline a second shield so that they have a small shield to cast on lots of different targets, and a big, more expensive shield to cast on a tank or anyone else taking a ton of damage.
 * Divine Spirit and Prayer of Spirit will be removed from the game. As Spirit will be the primary mana-regeneration stat, we don't want it to vary as much between solo, small group, and raid play. Blessing of Kings and Mark of the Wild will not boost Spirit either.
 * Mana will be a bigger consideration for all healers. We aren't trying to make healing more painful; we're trying to make it more fun. When the cost of a spell isn't an issue, then casting the right spell for the job is less of an issue because you might as well just use your most powerful spell all of the time. We are, however, getting rid of the five-second rule, because we don't want to encourage standing around doing nothing. We're also going to cut back on the benefits of buffs such as Replenishment so priests (and all healers) don't feel as penalized when those buffs aren't available.

New Talents and Talent Changes
 * We want to improve Discipline's single-target healing capacity. One key is to make sure shielding isn't always a more attractive option than healing.
 * We want to improve Holy for PvP healing. One way to do this is to make sure that Heal's throughput is similar between both specs.
 * We want to improve Shadow for short fights and reduce its susceptibility to school lockouts.
 * Discipline will finally be getting Power Word: Barrier as a talented ability. Think of it like a group Power Word: Shield.
 * We want to make Holy a little bit more interesting to play. One new talent will push the Holy priest into an improved healing state when he or she casts Prayer of Healing, Heal, or Renew three times in a row. The empowered state varies depending on the heals cast.
 * Since the Shadow tree has a lot of passive damage-boosting abilities -- something we're trying to avoid in Cataclysm -- we will need to replace several of the tree's talents. One idea is to play off of the new Shadow Orbs mechanic (see Mastery section below), possibly allowing you to consume an orb to increase damage from Mind Blast or reduce Mind Spike's cast time.
 * Misery will no longer affect spell Hit chance. We want players to be able to gear themselves around a Hit cap that isn't variable depending on group composition.