Yes, this is big-time thread necro. But I've recently come up with a big appreciation for this card, and while this article
remains great, there are some extra points I would like to get in here.
First thing I want to point out is that those supposedly rare cases where it is good with the discard-for-benefit stuff aren't as rare as I think you think. Well, I don't know, maybe they are really rare, but any time you have a decent engine, +buy available, and need or want a BIG source of money, you can make secret chamber work. I have more than one time used this trick, which people will sometimes talk about with scrying pool decks, where you discard a bunch of cards and then draw them all back.
The card is, as you point out here, terrible for big money. It can really shine, though, if you have an engine that will need to buy a good number of green cards for decent stretches of the game. Think an engine that needs silk road or gardens or dukes to win, for example. This card can really make it happen. While it's very much a nombo for slog decks like this, engines that go for them are a different animal. It's particularly good in decks with low amounts of treasure, which get most of their oomph from cantrips.
It's really good with copper trashing. With strong trashing, you are probably trashing the estates. But if you've got moneylender or spice merchant, going engine, this can be a very potent card. Also, it swings more normal trashing toward preferrentially going after coppers - for instance, in a lot of cases you will actually want to upgrade copper before estate when you have crossroads in the deck.
It's similarly good with stables. They can make the backbone of a very powerful engine, just the two of them.
There are some tactical nuances to be aware of. There's the trashing issues mentioned above, but also certain cards, basically sifters. Warehouse is the poster child. If you warehouse up some coppers and estates with a crossroads in hand, you almost always are going to want to discard the coppers. You will draw better back with the crossroads, particularly in any kind of deck where you have these cards, which will be an engine. This is especially true if you have some other sifter (another warehouse or cellar or something) to follow it up.
Here's a couple of games to illustrate some of the broken things you can do, in the right circumstances.
http://dominion.isotropic.org/gamelog/201301/10/game-20130110-155734-f6b9e214.htmlIn this one, the presence of other villages is very important, there's copper trashing to help get it going, secret chamber gives the cash, and woodcutters give the buy. 4 colonies, 2 provinces, a duchy and four estates in 18 turns, which doesn't sound THAT great, but the cool thing is that it's actually GAINING steam at the end, so it has great longevity.
http://dominion.isotropic.org/gamelog/201212/22/game-20121222-162124-894c1630.htmlHere, crossroads, stables, a worker's village for needed buy, and a couple golds, nets 5 provinces and 4 duchies in 14 turns. Pretty nifty!