[dasmoth]

Datomic doesn't seem to have had a huge amount of marketing: it's been spreading largely by word of mouth, so a slow build-up makes sense.

It does bring an exceptionally elegant design (well worth reading Nikita Prokopov's "Unofficial guide" if you're curious). Also, the time and transaction-annotation features are unmatched AFAICT -- if you're working with complex data where provenance matters, Datomic can save a HUGE amount of work building tracking systems.