I have used monstercommerce, os commerce, zen cart, cartweaver, x-cart, and some other smaller carts. I really don`t like any of them that much, but have ended up using x-cart the most because of some of the 3rd party add-ons that fit what my clients needed. The problems with all of them is their admin areas are very complicated for most clients. Yahoo might be the easist for clients.
They also don`t integrate very well with most brick and mortar inventory systems.
- a new media firm, providing ecommerce solutions, redesign consulting, web design, email campaign management, and internet marketing.