I'm using CouchDB to store (and serve) article ratings on my blog. It's not exactly heavy traffic but it's been rock solid so far.
Also planning on adding comments sometime which I'll most likely also store in CouchDB.
I've found it quite easy to get started with, on OSX you can just download CouchDBX to get started quickly. I use a Sinatra backend with RestClient to interact with 'the couch' through straight HTTP verbs and such.
Great fun.
