Neat. I actually prefer the "infix" style for operators (i.e. having the methods on the values instead of on the helper) and I'll see whether I can adjust AQB to support that.
Postgres 9.3+ is fairly straight-forward too. Here is go + github.com/mgutz/dat
// one trip to database using subqueries and Postgres' JSON functions
con.SelectDoc("id", "user_name", "avatar").
HasMany("recent_comments", `SELECT id, title FROM comments WHERE id = users.id LIMIT 10`).
HasMany("recent_posts", `SELECT id, title FROM posts WHERE author_id = users.id LIMIT 10`).
HasOne("account", `SELECT balance FROM accounts WHERE user_id = users.id`).
From("users").
Where("id = $1", 4).
QueryStruct(&obj) // obj must be agreeable with json.Unmarshal()
That said, the change feeds are pretty neat and RethinkDB is still a pretty exciting project to follow.
(Full disclosure: I wrote the ArangoDB Query Builder without any prior exposure to ReQL, so I may be biased)