I bought a playset. It will drop again once Theros block rotates out of Standard, so I'm being punished a bit for my impatience, but I wanted to use the card now.
Oh, it's not a functional reprint of City of Brass, though. Lots of cards can tap lands, and City of Brass deals damage in those cases. So if I'm facing Opposition or Icy Manipulator or whatever (in Legacy, it's most likely to be Rishadan Port), that can add some extra damage to me if I'm using City of Brass, whereas Mana Confluence only hurts if its ability is activated. And since City of Brass deals damage rather than requiring a life payment, it can be mitigated by damage prevention (such as Urza's Armor) and its ability can be activated even when one lacks the life to pay (perhaps under a Platinum Angel or Phyrexian Unlife). The two cards are very similar, to the point of being equivalent most of the time, but the differences matter in some situations. For most decks, Mana Confluence should be marginally better, although for budget gameplay, the difference between a three-dollar card and a twelve-dollar card is the more relevant consideration.