Its unfortunate that right now none of the 3 major document stores seem to be doing all that well or are easy to use straight out of the box. I use and like mongodb but only for prototyping. I havent decided what to go with longer term if my projects have a need. Couchdb is interesting but seems to be going through some serious growing pains right now with the couchbase product being very confusing to figure out and use. Riak is also interesting but it seems more specialty then a general purpose tool.
Kind of a bummer.