I downloaded and installed the 64-bit Mac OS X version of Couchbase 2.0.0 Release but I got a "could not connect to 127.0.0.1:8091" in the browser when I tried to open the Couchbase Admin Console to open up the installer/configurator.
The problem is that the first time I tried to fire up Couchbase was when the downloaded Couchbase dmg file was still in my ~/Downloads directory.
Then when I moved the dmg file to my ~/Applications directory, this prevented the Couchbase Admin Console from working properly.
What I had to do it to Quit Couchbase Server. (So you shouldn't see the couch icon at the top)
Then delete the ~/Library/Application Support/Couchbase directory. (Delete the Couchbase directory and its contents only!)
Then fire up Couchbase again from your ~/Applications directory.