I got to know one of the people (Jan) working on it a while ago (like 6 months) and have been playing with it ever since. I found the community around CouchDB to be both very knowledgable and helpful so that whenever I ran into an issue it was resolved in a matter of minutes or hours at least.
We just kicked off a project the other week which basically requires us to store data in the non-relational way and due to CouchDB's document oriented store we selected it as one of the technologies to use. So this is actually the first time that I will run it in production, but I'm still pretty confident about it. :)
Just an update here (2009-10-25):
Our first CouchDB install is 20 GB, it hosts 40 million records. It's been running in production since January 2009, and it's been great. Read (GET) speed is outstanding and we use it as a store for complex data, and then it's just pull.
Our second couchdb installment has two databases, one is 160,000,000+ documents (210 GB), and growing between 150,000-300,000 documents a day. The other is only 35,000,000 documents (7 GB). This setup has a lot more reads and writes and initial tests are performing very well.
View building on the 160,000,000 document database took roughly a week, but since then we upgraded to a larger Amazon EC2 instance and we are also getting ready to update to CouchDB 0.10.x (from 0.9.1) as this release includes a lot of performance improvements in view building.
