I tend to disagree that spell haste is useless for healers. Look at the progression Blizzard has taken with healers.

Molten Core: lots of stats, a bit of +heal, a bit of +regen, nothing fancy.
BWL: lots more regen, introduced fights where you almost *needed* to do a healer rotation.
AQ40: tons more regen, balanced with healing. Finally stressing Mp5 as a primary stat.
Naxx: +heal scales a little better, but even more regen. Finally have the holy trinity: 10k mana, 150 Mp5, and 1000 +heal.

TBC: continues.

Now, look at *encounters*. What does TBC suggest to all of you? From what I've seen so far (3/10 T5 bosses down), they think we have enough regen now (it's tapering off / plateauing), they know we have enough +heal (easy to break 2000+ if you want to), and they recognize that neither of those stats scales in a satisfying way.

So they stopped, and thought about what could possibly make us lose fights now. We have lots of regen (Super Mana + Shadow Priest + gear = win), we have lots of +heal (so we can downrank for more longevity, or switch to high rank for our highest HPS) ... but we still lose tanks to burst damage.

And they can't make more steady damage -- that's been done to death (hello Rank 2 Heal, *cough* Naxx *cough*). They can't do more huge damage (at some point, they're capped by the stamina of the tanks). So they're increasing burst-y damage. Medium-to-large hits, but many of them, back to back.

And how do you deal with that? Crank up your HPS. +heal is a decidedly BAD way to do that. So they introduce spell haste.

If a paladin geared him or herself in all the spell haste gear available in BT+, with 2/5 T5, according to the math I did, you get Holy Light down to about 1.65 seconds cast. With over 2k + heal. That's a 7k heal, in 1.65 seconds. And that's the type of encounters we're going to see past BT. Burst damage, then steady sustained, then BURST, then steady ... burst to force us to wear spell haste so we can DEAL with that damage.

My 2c, anyway.