libcouchbase is a callback oriented client which makes it very easy to write high performance, thread safe programs. If you're interested in the early history of libcouchbase you might want to check out the blog post
The key component of libcouchbase is that its asynchronous, giving you full freedom in adding it to your application logic. From using the asynchronous interface you may schedule a lot of operations to be performed, and then you'll get the callbacks whenever they are performed. I do know that there are a lot of people who don't care about an async interface, so you may also enable synchronous mode. When synchronous mode is enabled you can't use this batching.
You might want to read the blog post I wrote where I create a small example program and explains why we need to do certain stuff at:
Unfortunately for you we've later completely refactored the API, so when you've read and understood the idea behind the library in the above blog post you should read the following post explaining the rationale behind changing the API, and what you as a user have to do..
Please see: http://www.couchbase.com/issues/browse/CCBC
The developers of libcouchbase usually hangs out in the #libcouchbase IRC channel on freenode.net.