consistentHashKey returns the object that will be used to calculate the hash key (if you don't return a String or byte array it will apply MurMurHash to the serialized bytes of that object). I don't know how equidistributed is that, you should look at the "items" values you encounter -- those might quite biased.
Also, consistent hashing does not distribute totally evenly. See: http://en.wikipedia.org/wiki/Consistent_hashing
In short, the interval of hash keys is wrapped to itself to form a ring, and this ring is subdivided by random points (hash of the nodes) into intervals (buckets). These buckets can end up in non-equal sizes. Usually more nodes you have more "equal" they will be -- but this is not guaranteed.