Yes, it doubles charge damage, and since smite is a flat bonus damage like power attack and not extra dice damage, it multiplies. Note a Paladin in 3.5 can do all of this. The only difference is if he misses, he wasted that smite (disincentive to massive power attack to make absolutely sure you vaporize the enemy in one hit). With PF smite, he can just keep going after someone. And the Extra Smite feat's available. And his first smite attack on...half the things he's likely to use it on (evil outsiders, undead, evil dragons) will do even more damage.
I don't know, I don't think I like the power level of it in PF even without all the 3E splat book fixins' (there's also the possiblity of obtaining pounce in 3E, so you can full attack with all that crazy damage). Seems to me like PF smite means you can't have BBEGs anymore, and instead need a BBNG to pose much of a challenge to the party.