Actually the talent is very very good for PvE (because of haste, allows you to skip haste when you are started gearing) and not so much in pvp (it's good but there are much more useful talent around which require less talents to spend)
I assume you're talking of discipline PvE, for which yes, there is no other option at all. Just out of curiosity I tried to mess a build without Enlightement, practically taking Absolution and Silent Revolve instead, just to get higher on the tiers. Taking useless stuff instead of useful. No.
It's not that useful, but 5% stamina gives some survivability through random stuff you encounter, 5% haste can be nice, altough it's not my favorite stat, far from it. And 5% spirit, well, it gives some extra mp5 to further ensure my manapool's safety [altough lately I've been thinking of popping shadowfiend just for the DPS, not for the mana..]
It's not that good talent, as our middletiers lack good talents, but it's still worth it.
In beta they nerfed it, by taking away the 5% int bonus. So now it busts 2 stats that disc priests value the least unfortunetly. I think this talent would be a lot better buffing spirit and int, or just int... stam is nice but easyly the last stat we look for as a healer, and 5% spirit is good for holly, but not for disc, disc stacks int and mp5... Int is the most importat stat unfortunetly...
As for the 5% haste = pure win. Can't say a word against it, especialy that disc gear generaly lacks haste, focusing mostly on crit/sp/mp5. So having a haste buff from talents is nice.
As you see from what I wrote, Enlightment seems like a very, very solid PvP talent, right?
More stam = more chances of surviving the massive burst in arena.
Spirit = the pvp sets have spirit = more mana for those long fights when you manage to survive the massive burst.
Haste = faster heals, shorter GCD's = did I mention it helps you survive the insane, massive burst in arena?
The joke is, that you CAN NOT take this talent for PvP... I have seen some priests with it, but you just don't have the talent points for this... there are lots of more important talents in the Disc tree...
Good PvE talent, tho it would be better buffing int, but worth it for just the haste. Not much choice anyway.
Very good PvP talent, but you can't have it, go reroll pally (joke). Or DK (sad joke).