CouchDB supports ad-hoc queries in the form of 'temporary views'. The downside (and I think a difference compared with MongoDB) is that temporary views can't be used in production since they are not indexed and thus are much slower than permanent views.

I'm developing my application in Python, which has great support for CouchDB in the form of CouchDB-Python (http://packages.python.org/CouchDB/) and CouchDBKit (http://couchdbkit.org/). Using CouchDBKit, it was pretty easy to set up CouchDB artifacts (map functions, reduce functions, design documents) into a nice file/folder hierarchy and write the simple Python glue code to deploy updates to CouchDB via a single shell command.

so far we're going with couch and haven't experienced this. the best part of course is that we can add items to documents on the fly whilst keeping the existing test data! this is major for us. we can go back to testing right away. with MySQL the changes were so major that it was better just dumping and recreating from scratch (we are using django) and this wasn't exactly fast. django has a project "south" that would help with this, but we're eventually deploying to oracle and cannot rely on it or have the time to extend it to properly work with oracle.