It's true that the definitive guide is a little dated now. A couple of points to pick up on:
Document conflicts: replication will pass conflicted document revisions (see http://wiki.apache.org/couchdb/Replication_and_conflicts for more detail and a comparison with Git). There is a limit on the number of conflicted revisions that can be stored for each document though (configurable, but I think 1000 is the default).
re, CouchApps, the intent here is to provide an easy way to distribute data visualisation / browsing apps alongside the data itself, i.e. you can replicate data and the tool to view it between CouchDB instances. They just provide a way to serve up static assets so, for most cases, it's no substitute for a proper web-application tier. As previously mentioned, there is now support for URL rewriting and CORS.
Also, CouchBase is far closer to MemBase than CouchDB. The original plan was to use CouchDB as a persistence layer but, as I understand it, this was abandoned. At this point they should be considered totally distinct, the naming being an unfortunately historical artefact.
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A few points...
Document conflicts: replication will pass conflicted document revisions (see http://wiki.apache.org/couchdb/Replication_and_conflicts for more detail and a comparison with Git). There is a limit on the number of conflicted revisions that can be stored for each document though (configurable, but I think 1000 is the default).
Clustering: The dynamo-based clustering layer used at Cloudant (BigCouch) is becoming a core part of CouchDB (see https://blogs.apache.org/couchdb/entry/welcome_bigcouch).
re, CouchApps, the intent here is to provide an easy way to distribute data visualisation / browsing apps alongside the data itself, i.e. you can replicate data and the tool to view it between CouchDB instances. They just provide a way to serve up static assets so, for most cases, it's no substitute for a proper web-application tier. As previously mentioned, there is now support for URL rewriting and CORS.
It's possibly worth mentioning CouchDB-Lucene (https://github.com/rnewson/couchdb-lucene) as well. This provides full text search - handy for many use cases where map-reduce is not a good fit. GeoCouch (https://github.com/couchbase/geocouch/) is also nice for GeoSpatial indexes.
Also, CouchBase is far closer to MemBase than CouchDB. The original plan was to use CouchDB as a persistence layer but, as I understand it, this was abandoned. At this point they should be considered totally distinct, the naming being an unfortunately historical artefact.