I was nervous writing that sentence, because it's hard to be sure of the truth of any claim to be 'first'! But none of the examples you mention, to my knowledge, provide multi-key ACID transactions. A compare and set facility for an individual key/document/row/entity group/etc is a very useful feature, but cannot be used to provide atomicity or isolation for transactions that read or write more than one key.
We plan to write something longer talking about the different levels of support that various products provide for A,C,I, and D.
> But none of the examples you mention, to my knowledge, provide multi-key ACID transactions
If you see it that way, you are right. The guaranty is just for one key/document pair (the key can be a key vector though). There is no way to have a commit over several key/document pairs with these databases.
If FoundationDB can do that, it is a big plus. If it can do it in a cluster, your product will have a great future.
Bigcouch and Couchbase are around for a while. There is also CouchDB (without the scaling).