Since these questions will inevitably come up:

  - You fsync yourself to ensure durability.  I can't see at a glance 
    what fsync settings are used for the speed tests.
  - It's not transactional, although single operations are atomic.
  - Indexes operate on a single-writer, multiple reader basis.
  - No traditional joins, although you can of course write
    a procedural function that joins for you.