I am a big fan of haste rating myself.
As you can see from my profile i tried to get alot of hasteproc effects together.
dragonspine, abacus (no proc ofc

), double mongoos, thundering skyfire in headpiece.
And I have to say it is pretty amazing, I am almost always under 2.0 Attackspeed, sometimes getting as low as 1.15 with the mainhand (bladefury+snd up, no heroism).
Together with the new swordspecc my dmg has gone really up. If I get a lucky procc streak with haste and combat potency I am limited by the GCD to spend all the energy I gain, i call it my "Small AR"

.
I don't know excactly how SwordSpec is treated (ppm, or flat %), but tests with and without haste items have shown, that the faster I attack, the more swordspec proccs i get.
I am really looking forward to all that fine leather pieces from BT and Hyjal with build-in haste rating.