I also did not know this existed. In case anyone else didn't know amazon.cn is the Chinese Amazon. Similar to amazon.co.uk, amazon.co.jp, etc, and the many other amazon divisions. As far as I know you will have to create a new account for each one as they don't carry over (or they did when I bought from Japan).
Hopefully someone else will be able to say how well it works. I will bet that the service will be better, but the prices will most likely be higher than on an ebay like site.