I'm posting this BEFORE I read this thread. That way I can go back and see how many people agree or disagree with my unvarnished initial impressions.
1. It uses wisdom. Kind of expected Int. This isn't a big thing.
2. It uses chainmail! I really didn't expect this, but I like it. Know what this means? "Wears heavier armor" is basically a sub-characteristic of the divine power source. Expect to see the Avenger in chainmail or better.
3. I feel like their channel divinity powers are better than the cleric's. Practice makes perfect, I guess?
4. Interesting Covenant powers. I like them. Simple, but interesting, and you'll see them a lot since they work on every encounter and daily power. I hope the Covenant of Wrath power doesn't get wacky at high levels. If there are a lot of Close Burst 8 type powers at higher levels, that could be an awful lot of additional damage.
5. 5 at wills is nice. They're all fairly useful. Vanguard's Lightning is useful, but only if you are really slick tactically. Otherwise, it doesn't do enough damage to make up for part of the damage being situational. Divine Lightning is pretty nice.
6. Blades of Astral Fire. Nice, but in general, I'm not a fan of AC or Attack bonuses that scale with level. They don't need to! +2 is just as good at level 1 as at level 10. At least it doesn't scale very much. These don't unbalance 4e, they're just unnecessary.
7. Angelic Echelon. Its themed like a summons, but is basically just a spell. Still, if the overall class has a lot of these, and has one or two summons that stick around for a while, a summoning flavor will be possible. We can't really know until we see more, unfortunately. This sort of "summons as theme for otherwise regular spells" thing will feel inadequate to me without at least some wizard style summoning with Sustain Minor.
8. Binding Invocation of Chains! Ok, I really like this one. Its different. No damage. HUGE area of effect. Decent action denial if you catch your foes in the first round of combat and you over power them in ranged versus ranged attack.
9. Purging Flame has really high damage. I wonder how many players will notice, since realizing it takes a little math.
10. Summon Angel of Fire. Ah. Now we get to the real thing. The only unclear bit is movement. I assume the angel moves on its own, on your initiative? The angel is unkillable, which I guess is a necessary concession to not including full stat blocks in powers.
11. Emissary of the Gods is the first power I can think of to explicitly reference the skill challenge rules. I think I'm cool with this. I don't use explicit skill challenges often, but the power still works, and I can roll with it thematically. "You don't gain a failure" will just mean "the target doesn't get upset at what you said."
12. Shroud of Awe is Shroud of Awesome. I have this mental image of a desert city with minarets, and every day at noon, Invoker Initiates climb each minaret and bellow out a call to prayer using the actual Voice of God.
13. Wall of Light is extremely good. Like, really, really good. Maybe too good? Its got some of the good things from Consecrated Ground, except in a bigger area of effect, and three levels earlier.
Overall thoughts?
I like it. Its playable. It wasn't something I was dying to play, because I like clerics more and they're similar in archetype, but it looks like a fun class.
Should hopefully satisfy those who want to play spellcaster clerics with more offensive spell selections.
Kind of wish they used holy symbols, so that there would be more multiclass synergy with the cleric, but that was probably a conscious design choice. Otherwise the classes might run together a little too easily. And its not like spellcaster clerics don't have a free hand to hold a staff or something.