I've started using NoSQL with an ACID-based system by storing the document revisions (e.g, modified invoices, purchase orders) into a NoSQL database with the SQL database holding the master data. We store document revisions so if we were to ever audit modifications of the invoice, we could pull up the very first version to the second, third, nth revision of the document. Meanwhile, we still keep master data on SQL database.
Sounds like you are doing what we are doing. Testing the waters, evaluating how NoSQL technologies fit into your architecture, and testing your problems against NoSQL solutions.
I'm still a bit wary of using NoSQL, and we store document revisions (e.g, if I modified invoice 1021, the lastest version would be updated in SQL, and the last version would be pushed into NoSQL) into SQL just in case (by using a draft_id column).
We need to see if our software is still deemed auditable by accountants since they have very strict guidelines on how a document trail should be stored.
