The opinions in sum (whether they are valid or not):
A. This isn't fair, other armor classes have plenty of drops with spirit.
B. This is a nerf to priest mana gen, though the opinion on how much varies.
C. It's going to be a pain because any spirit gear we get must be from a vendor. A lot of it also has crit, ew.
D. There's more spirit per piece of gear, so we don't need spirit on as many pieces as we did for 4.0 raids.
E. It's going to take priests longer to gear up than other healing classes.
F. It's one of the ways to keep priests from getting into Wrath level mana gen so they can't go back to bubble and FH spamming.
G: WAH. I WANT MY SPIRIT. WAH.
H. Now we have to roll against DPS on non-spirit gear! (Nvm that DPS rolled on spirit gear before.)
I. YAY throughput-gear for me!