I personally don't have a big styling preference, but I think it would be nice if Drake's overall codebase was consistent. We currently don't use extra spaces, don't leave hanging parenthesis and try to put ```let```'s pairs on the same line. So this function would look something like this:

```
(defn- s3-bucket-key 
  "Returns a struct-map containing the bucket and key for a path"
  [path]
  (let [bkt-key (split (.substring path (count (re-find #"^/*" path)))
                       #"/" 2)]
    { :bucket (first bkt-key)
      :key (second bkt-key) }))

I don't want to appear nitpicking - I hope it makes sense to try to maintain a consistent code style across the base. 

What do you think?