I also have an attack card named Infiltrator that interacts with the Tavern mat:
http://forum.dominionstrategy.com/index.php?topic=15041.0. Great minds must think alike.
Question to this card: I assume that each player has multiple infiltration tokens available, in case they play multiples of this?
Mechanical observation: Do you need to have the Infiltrator go on the Tavern mat, when the Infiltration token is already there to mark the effect of the attack? If you don't, you can simply have 10 Infiltrators in the supply instead of up to 60.
General Comments: That said, do you need the Infilatration tokens or the Tavern at all? You could greatly simplify this, without massively altering the effect, by simply having its effect be:
+2 Cards
Each other player takes his -$1 token.
Trash this.
Gain a Gold.
I realize that this takes away the attacked players' decisions, but I see that as a positive, for three reasons:
--it takes out politics (where they choose to let one player have their Gold but not another)
--this card becomes massively OP in multiplayer (in a 4 player game, play this to eventually gain 3 Golds)
--rarely will a player choose not to lose the tokens, because there's little value in continually attacking yourself
This seems like a decent attack; you'd have to playtest to see how it compares to Soothsayer (as a Gold gainer), Pillage (as a one-shot attack), and Relic (as something that provides money and attacks with a penalty token).