After recent events I've been looking for a market that takes bitcoin multisig seriously. Sourcery is new and vendor selection is still limited, but its implementation of multisig is by far the best I've seen.
Three main reasons:
Most markets have you send your BTC to an intermediate address, take their cut, and then forward the rest to a multisig address afterwards. That means you have to trust the market to forward the bitcoin, though. During the last day or two, HANSA was just funneling any bitcoins they got to LE, and there was no way for buyers to know. Sourcery gives you two addresses to pay: one for their cut, and one that goes directly into a multisig address whose redeem script you can verify on coinb.in.
With 2-of-3 multisig, you have three parties that can sign the transaction. One should be you, and another should be the vendor. With a redeem script you should be able to verify your address is in there. Verifying the vendor requires an extra step that only Sourcery has implemented. Basically, they have the vendor sign a huge list of their addresses with their PGP key, and then you can verify that the address on the redeem script is on that list.
They use your wallet's master public key, so they can cycle through destination addresses when generating transactions. This makes it harder to track a single account's transactions, and I think reduces the chances of a redeem script collision. (Frankly don't understand that one too well...)
So far I made one purchase and I was able to verify my address was in the multisig redeem script. Vendors don't have many reviews yet, but you can cross-check them against Grams Infodesk to make sure they're legit. Grams Infodesk doesn't monitor reviews for medium-to-small-sized vendors, so sometimes you gotta check out the linked Dream accounts to see if there are reviews there.
This is a market I've had my eye on for a while now, seems promising. Thanks for the field report!