Fool's Gold is a very interesting concept. Some analysis:
- Chapel/BM probably got a lot faster (like possibly dominating strategy) if Fool's Gold is out. Chapel/Fool's Gold and not buying any treasure but FG is going to be fast fast fast, I think. If you're doing nothing but buying Green, 2 FG get you a Duchy, 3 get you a Province, just like regular Gold. But you can get them in your deck much quicker.
- Talisman/FG is also potentially interesting, though unlikely to be sufficient on its own without help. Chapel still seems best, but any sort of big draw, +buy engine can also expect to do very well with FG.
- FG seems like Native Village in that it's a card that can be very good if you build your deck around it and terrible as a casual acquisition. added: That said, because the card benefits so hugely from density, FG might end up being a lot like Minion - if your opponent starts pounding the pile, you might have to as well. A deck with only 5 treasures probably isn't going to hold up very well for a green rush.