We're talking about a few DBs here, but I'm just going to focus on Cassandra, as Mongo is a lost cause, and I don't know much about HBase. However, my arguments apply to all AP systems with tuneable consistency.

I think you're saying that people use Cassandra with consistency=ALL everywhere to get strong consistency? In that case, sure, then they should look at something else. Potentially even the database your company produces. However, that is a strawman; Cassandra was designed to be an AP system. Later additions like tuneable consistency and lightweight transactions are a compromise, and implementing something as crazy as ACID transactions on C* would be insane. Like, totally stupid. It is so far from the core goal of an AP system, that I would be very worried about the leadership of the project.

I like my databases to do one thing, and do it well. That's why I like basic C*: it's an awesome AP KV database. Features that have been added later have generally been syntactic sugar (CQL, indexes, multi column indexes, user types), or compromises (tuneable consistency, lightweight transactions). But it still remains an AP system at heart. And because of that, ACID transactions would _not_ improve the product. It would all but destroy it.

You should probably mention that you were a founder of FoundationDB if you're going to comment on articles about it.