Based on the research I've done, it seems like in the asp.net world you have two divisions for E-Commerce software:
- Storefront Systems
- E-Commerce Frameworks
Storefront systems - at least how I've categorized them - are intended to be used for typical shopping cart scenarios (i.e. you have a single site with items you're selling and people can put those items carts and purchase them). You can definitely extend them to do other things, but they do have limitations.
Storefront systems have lots of out of the box features. These systems are also more complete and ready to run immediately than frameworks.
Frameworks are built to be extended. You can usually run a basic site out of the box, but you will almost always modify it - adding features and customizing it to fit your needs. Frameworks are to be used when you require a multi-site/multi-catalog system or when your requirements are so different that the flexibility of a framework is desired. Frameworks also seem to be ideal for situations where you would normally build from scratch, but you prefer to have a good starting point that has been well-tested.
Frameworks are much more expensive to license than storefronts.
On the storefront side, it's been pretty easy to find people willing to talk about their experiences with different systems. So far - based on the reviews I've read - AbleCommerce and ZNode seem to be the best options. The reviews I weighted heavily came from developers who were paying particular attention to how easy the systems are to extend - and how active the particular developer community seems to be.
On the framework side, it's been difficult to find reviews that weren't published by the originating company (Matt Moore's post above is an exception). It sounds like MediaChase ECF G5 and Microsoft Commerce Server are the standard-bearers in this area - with Aivea Commerce Server a relative newcomer.
My take on this is strictly based on researching online opinions and reviews - as well as discussions with sales folks. I've also done demos of the various systems and installed a few on test servers.
I'm I off on this? I'd love to hear more from people who have actually implemented one of the framework systems.