1. Map Reduce view -- just throw some mr function you will find out the document which it preserved
2. Web UI (the futon) it alleviate lot of Admin pages along with lately added security is good enough to manage it
3. Hot data backup, it is an excellent feature and makes like easier
1. Mindset of treating CouchDb as all in all self contained product and hence lacks native interface, (there are APIs but it is based on http -- even http world is moving to websocket due to its inherent limitation for certain usecases, having Database served by http to another middleware is costly and environmentally hazardous like gas guzzling trucks
2. lack of native search (full text) but there is a lucene based one but already couchdb is dependent on JS, Erlang, ICU and having Java into the fold is kind of nightmare to the mix but it works and also gives head ache when replicating and spinning multiple nodes
3. It is not truly distributed but it is kind of storage engine which can be equated to better dets storage engine or innostore but there is nothing similar in couch architecture to be comparable with Cassandra or Riak.