THey are easy to work with, transparent, and affordable
Being a small company resources are limited, so project managers can sometimes be spread fairly thin. That means response time on issues runs between nearly immediate and... days.
There are two levels of products, at least. A flat file product catalog database and a full-bore configurator tool. If you go with the Catalog tool, just be prepared to do some compromise on your ideal, and/or be willing to pay for some extra custom work if you want to push the product - whether by CDS or one of their partners. Don't expect the catalog product to work like a configurator if that's what you really need. Its a selector and shopping cart - a powerful one but still with limitations. If you need to configure highly complex product, then you'll need to pay up for the full configurator. But do your research with respect to your real need. Overscope and you will pay more than you should. Underscope and you will waste money and time while you gradually realize you need a more powerfull tool. Fortunately, CDS is honest and very helpful in assessing up front what level you need to buy into. The same goes for any of it's competitors. CDS is in my view the best solution for the money. This is my second time using CDS, and I'll come back again.
We are converting a site to a dynamic catalog with a built in shopping cart, abandoning a static and very un-friendly (for the customer) and SEO failure product list that is PDF-dependent.