the spell haste is the best thing for raid healing, and is amazing for tank healing. haste means that you can use greater heal rank 1 rather than flash heal. with the 2/5 set bonus from tier 5 it makes healing with greater heal even more efficient.
with the changes to spell haste in patch 2.4 spell haste will reduce the global cool down to a maximum of 1.0 seconds from 1.5 seconds. spell haste is under rated by a very large number of people for healers.

while I do believe spell haste is great for healing, I do understand that some fights require a lot of regen. my advice is to make 4 sets of healing gear; 1 for pure +healing, 1 for massive mana regen, 1 for spell haste, and one for stamina(8k min for tk/ssc and 11k for bt/hyjal). understand which fights to use which gear set. there is no 1 gear set that is perfect for every encounter.

I rarely shard any of my healing gear because rarely do you find a pure upgrade, every item offers different statistics that are important for a different encounter.