Continuing to work on my little project.  Mostly messing about with UI and getting CouchDB to do what I want it to do.  The query mechanism is a little weird when you're used to SQL(Alchemy) and complex referential schemas.  For instance, say you want to be able to total votes across M objects with N users able to vote up/down (once) for any given object (and you want to be able to restrict the search to a single query).

{ 'type': 'vote', 'survey':'surveyname', 'target': targetid, 'vote': -1 }

The map function is pretty straightforward, you extract the keys you want to query against with the vote-value like so:

function (doc) {
    if (doc.type == 'vote') {
        emit( [doc.survey,doc.target], doc.vote );
    }
}

The reduce function is where it gets interesting. CouchDB will potentially *rereduce* your partially reduced values, so you need to be able to handle both direct summing/counting and summing partial values in your reduce function:

function (keys,values,rereduce) {
    var sum = 0;
    var count = 0;
    values.forEach( function( v ) {
        if (rereduce) {
            sum = sum + v.sum;
            count = count + v.count;
        } else {
            sum = sum + v;
            count = count + 1;
        }
    } );
    return {sum:sum,count:count};
}

Works reasonably well, but I'm still finding myself wanting to do "joins" so that I can retrieve the vote counts when I retrieve the "target" objects. Haven't found the equivalent of that for CouchDB yet.