Definitely the best episode of the three parter so far (which definitely got progressively darker).
And ya know, these Ori are the first SG villian to really be truely frightening- and it's not just the Jeremy Irons looking fellow either.
The idea of religious fanatics and (insert religious text of your choosing)-thumpers actually being able to wield and inflict the "righteous" power of their doctrine to enforce their beliefs upon people is truely terrifying.
And the fact that they have the ability do so upon fairly advanced and educated civilizations really steps them up a few notchs from the Goa'uld, who relied on more primitive and ignorant societies to achieve the same effect.
Add to that the "pretenders" vs "true-believers" aspect pointed out by otehr posters here, it adds up to one scary big baddie
"Hey- what the hell are you doing here?"
"Nice to see you too."
"Well, I suppose after you've saved the world 7 or 8 times..."
"Well, who's counting?"
"Teal'c, actually...he mentions it quite a bit."