Sorry, I'm going to make an assumption that by interface difficulty you mean it's ability to be queried (map reduce only + lucene {optional})? Also, nothing for

Sorry, I'm going to make an assumption that by interface difficulty you mean it's ability to be queried (map reduce only + lucene {optional})? Also, nothing forces you to use protobuffs, you can tell riak what (via the content type of an http header) what your data is and get it back as such. I don't see that as a weakness.