I recently completed a project for a labour union, which required a robust pre-registration verification process, which the CB team helped me develop.
That doesn't sound very special on its own but having the confidence to have the team behind you when you are doing something for the first time just means everything.
The functionality is intuitive and the support that I have had from the developer for custom additions has been second to none - we now use this extensively across most of our clients' ecommerce sites.
If you need discount coupons and promotions to work on your site - particularly business to consumer - you really need this component to make your life easy and your client's happy.
Most importantly the component does what it says on the tin, we are in the process of applying it to all our clients' sites.
When we have had a query, the support offered has been timely, professional, courteous and complete - I recommend this component and RSJoomla to anybody running a professional website.