Costco has a new line of dish soap under their house brand, Kirkland Signature.
We tried it—even though that meant buying more than a gallon of a product that we didn't know if we would like.
Our experience so far has been positive. The contents of our bottle have a light grapefruit scent, and thankfully not the cat pee smell that a commenter over at Mom Go Green griped about. It cuts grease well, and the price is right; we paid $7 for our giant jug.
Our complaint is the same as it usually is: what's in it? It's not listed at GoodGuide. Costco is forthcoming about what's not it the detergent: phosphates, dyes, optical brighteners, or bleaches. They're also not tested on animals, and they "feature" biodegradable cleaning agents and plant-based formulas. But are they entirely free of petroleum products? Other than the bottle, which is still (petroleum-based) plastic, it's hard to say.