I'm not sure how useful SQL is without joins though... I can see that this might be interesting to test against, but don't think SQL is much simpler than a lot of the query engines for non-sql databases... Until you get to joins, and similar operations.

Right now, I'm most interested in seeing RethinkDB see more traction... it seems to have most of the features I look for, and I, for one don't mind more programmatic queries, and the management interface is really second to none at this point... MS-SQL, I'd probably consider a close second.

For one, just indices in a strongly consistent distributed store, with ACID, is a big deal. Doing this yourself with another strongly consistent DB is a massive error prone PITA.

Plenty useful -- we have SQL-like query tools at work (which operate on SSTables and ColumnIO) that I use extensively nearly everyday and I almost never do a join. Just SELECT and WHERE gets the job done 98% of the time for me.

I can see many of the exploratory data analytic can be done without joins. Well, my experience could be too specific though.