Forager works extremely well with cultist, turning into a grand market with extra cycling. You get +3 cards, +X money (by the time you start trashing cultists, you should make sure to have a silver in the trash), and get an action all to boot. When you've won the ruins war this is a great way to get rid of excess cultists. Also, Forager is much better in games with junking attacks, such as ruins. In games with additional kingdom treasures, forager shines even more. Loan is a great example, speeding up trashing while also adding a new unique treasure to the trash. Spoils is also an option, but unless you have a way to keep up with the trashing of forager, I doubt it would be worth it.
Now we come to the tricky portion. Like City, Forager can "level up" as the game goes on--and just like City, the leveling is equal for everyone. It's not worth any money until at least one Treasure, probably Copper, has been trashed with it. And if you trash a Copper now, your opponent can trash an Estate next turn and get a free $1 from your trashed Copper. Each trash of a new Treasure with Forager is a bit of a gamble... if your opponent is also going after Foragers. If you're the only one going after Foragers, though, you can get away with trashing higher-power Treasures--just be aware that your opponent is $3 away from picking up his/her own Forager.
I think that while this is something to think about, it isn't overly important. If your opponent does not have a forager, than it is beneficial to try and "level up" your own foragers to at least +1. In my games I found that trashing a copper early (sometimes even over estate) is better than waiting to burn through your estates to trash coppers.
Forager is what Trade Route tried to be. It is easier to activate, trashes much quicker due to being non terminal, and gets to be a powerful source of money later in the game. Because it's non terminal, it's a safe pickup in any game that includes non draw junkers. All in all, one of my favorite 3-cost cards. I am inclined to think that it should cost 4, just because in 95% of all cases, it's straight up better than Trade Route.
