This is where I think a lot people disagree with each other.
To me, and I suspect to many others who think the comparison is valid, 4e's at-will, encounter, and daily powers seem very much like CRPG/MMO power cooldowns, and much more so than 3e did.
I'm not an expert on WoW, but having played a decent amount of Guild Wars in my time, I can say that it feels very similar. You have your powers you can spam more or less all the time, your powers that you can pull off periodically in the fight, and powers that you can only pull off once in a fight, all achieved via cooldowns. Obviously 4e scales it slightly differently (and for all I know, WoW might too), but it still seems very comparable to me.
The reasons I don't think that the same can be said for 3e and earlier are twofold:
First, it didn't apply to every class. Spellcasters had a cooldown mechanic via Vancian casting, but fighters and thieves didn't. This is in contrast to CRPG/MMO practice where it's a defining characteristic of the entire combat system.
Second, there were no tiers of cooldown. You cast your spell, and couldn't cast it again until the next day. A defining feature of the MMO combat being discussed is that different powers have different cooldown times, which becomes an important tactical element.
Basically, while you're correct that 3e had some MMO-like cooldown aspects, I feel that 4e is MUCH more similar in that regard. Not identical, but much more similar.
*Chuckle* I like this discussion.
But that's the thing resistor. As you alluded to, many other people are scratching their head when people equate encounter powers with cooldown.
Encounter powers are HORRIBLE analogs for cooldown since as you pointed out, you can cast a cooldown power multiple times in a fight as long as the fight goes on.
If you have a cooldown of 5 minutes, and the raid last 30 minutes (definitely on the low side of BBEG in the high level areas), you're getting at least 5 castings of that power.
That same fight in D&D, you're only casting your encounter power ONCE and that's it. Hell, one of the complaints about 4e _IS_ the fact that encounter powers don't recharge in a fight a la ToB.
In a fight scenario, a 4e character really has only two options.
1. Pull off an attack they can do at will
2.
3. Pull off a once per fight manoeuver.
So how does this make encounter powers akin to cooldown?