I'm coming around on Cache. A gold at 5 can be really good in, for instance a Grand Market race, and if those two coppers are, for instance, fueling a Spice Merchant engine, then OK. (Granted I'm not going to try to make a Spice Merchant engine if there's any more viable method.)
Also, excellent counter to Noble Brigand. If you have Caches instead of Gold, that player who's spamming NB has nothing on you. And if he's flooding your deck with copper anyway you're not going to notice two more.
And in a Gardens game? Three money cards in one buy?
It's highly situational, and there are many, many games where I will ignore it and wait to hit 6 for the Gold, but it's not by any means a terrible card.
As for Noble Brigand itself, speaking as a player who plays mostly 3-player, it's a pretty mean card and here's why. In a Pirate Ship fest, I will buy no money and rely on virtual money in order to cripple the opponents PSs. I do the same thing in the rare event of an aggressive Thief player. But that defense is useless against NB. If I have no money, it floods my deck with coppers, which is like a cursing attack that never ends.