yacin

Nobody runs an oscommerce site without installing at least a contribution. Contributions are features contributed by the community. Key functionalities in Oscommerce are implemented as contributions (Paypal WPP, UPS, coupons etc ...)
The problem with contributions is the way you install them. You have to hack several core files, but there is no cross-dependency mechanism to help determine if a contribution is compatible with the ones you've already installed.
After installing several contribution, you basically end up with a system that you can't upgrade by moving to a new release or by installing further contribution.
I like Oscommerce, it's perfect to build a basic ecommerce site, but iI think it fells short as a foundation to build an advanced, customizable, maintainable site.
My 2 cents