We have been using C&S since it was first available, first using it for the added tracking to our own packaging and then the eBay satchels. The site is sometimes temperamental but the benefits outweigh the few problems we've had. The flat-rate boxes can take up to 15kg and are definitely a cost saving.

The eBay postage labels are supposed to be available to all users soon so you will be able to do labels for the flat-rate satchels and boxes without logging in to the C&S site.

More info

http://sellercentre.ebay.com.au/news/australia-post-labels