I think it looks rather decent. A lot of people deride the "dress" surcoat/cassock, but I rather like them. It makes paladin armor recognizably different than warrior or deathknight armor. It also plays up the "cleric" aspect of the paladin.
The helm is clearly inspired by T2, Judgement armor. In fact, where T2 was Paladin as Dark Inquistor, this set is Paladin as Fiery Inquisitor. Which is a pretty neat interpretation.
What's most interesting to me is that Blizzard did not show off any recolors of the set. And because the T12 theme is fiery armor, I don't see how they can actually do recolors this time around without wrecking the theme. So it will be interesting to see how, or even if, they differentiate the heroic version from the normal version.
My final verdict is that T12 is not in the absolute top Paladin sets (reserved for T2 and T6), but it is certainly above average.