I've been doing alot of resto shammy reading lately as my own shammy nears 85 (<3 watery heals) and since the other "are you ready for raiding" thread derailed somewhat, I decided to post some resto shaman specific stuff that I've found here for those of us who like nothing more than empty buckets of water onto people's heads.
So, stats to aim for pre raid:
1) ~2k spirit
2) 916 haste (this is a bare min value, do not go below) assuming you have Wrath of Air, which you will.
3) Trinket with a spirit proc, (pref Tear) and the epic badge trinket. (this is your first VP purchase) This may change in 4.0.6 with the change to mana tide totem - I'll keep looking when the implications of that change become clearer
4) After you reach these points, you then stack either mastery or crit. Which you go depends on different factors. (Will mention in abit)
To quote Jynus:
Int is your prime stat. You gem for it, you gear for it. You take the gear upgrade that has more int, and reforge the stats if need be to suit yourself. The more int the better. Int is the new haste.
The 916 haste value is there for a very specific reason. With Cata there has come a new concept in gearing, and that is "haste breakpoints." Essentially, a haste breakpoint is the level of haste at which your hots gain an extra tick. At 916 haste, Riptide, Earthliving Weapon and Healing Rain (all your hots) will have gained 1 extra tick.
The next breakpoint for haste, at which all of your hots will gain a second extra tick, is not reached until 3051. This is pretty much not achievable in current gear without sacrificing too much in the way of other stats, so don't bother. Get 916 haste, then favour your next best stat.
Crit vs Mastery is an interesting one. EJ is starting to argue that Mastery for Resto Shaman is not bad, infact, it is decent, but only at certain points. Here is the breakdown:
When target is < 100% hp: Mastery is better than haste for HR, Riptide, UE
When target is < 80% hp: Mastery is better than crit for HR and CH
When target is < 62% hp: Mastery is better than crit for single target heals
When target is < 44% hp: Mastery is your strongest stat period
So, with that in mind, we can work out how good mastery will be based on what we are planning to do. In 5 mans / heroics, and 25 / 10 normal mode tank healing, crit will almost always be better than Mastery. The reason for this is that mastery is effectively just a flat healing boost. Crit does exactly what mastery does (increases your healing done), but it also grants Ancestral Healing procs, Ancestral Awakening procs and mana returns from Improved Water Shield. The 10% damage reduction is exceptional when tank healing, and so you want enough crit to make sure this is always up - plus crit improves your HPM (healing per mana)
If you are engaged in hardcore 25/10 man progression raid healing then there is a case for saying that Mastery is a better stat. Again to quote Jynus:
a LOT of the encounters follow along a path of completely destroying the raid to near death over and over. Even with crit affecting your hots, the overall benefit from mastery on your HR and CH powers through this and gives your heals a completely hax level of healing done. For these types of encounters where you're constantly healing people at or below that 50-60% threshold, mastery is easily your best stat. So stack it to the moon over crit.
I would say that for us, crit is probably a better stat to gem for once you have reached the 916 haste breakpoint - it is certainly what I am going to do. Stacking Mastery is the kind of thing you would do if you 100% knew you were going to be always raid healing, and working on hardmode progression. I think for our style of raiding at the moment, crit is probably more useful as it is more balanced - stacking mastery is a kind of "all your eggs in one basket" type of approach.
Oh quickly, on the issue of gemming - it's easy:
RED: 40 int
YELLOW: 20 Int / 20 crit OR 20 haste OR 20 mastery (depending on what you are doing, following the guidelines oiutlined above)
BLUE: 20 Int / 20 Spirit