What do you like best?
The admin interface is better than those of other CMS platforms I have used in the past, such as an older (2009) version of DotNetNuke. The intuitive layout makes it easier to devolve content management tasks onto less-technical coworkers. The Kentico E-commerce module is intended to work as a self-contained online store system.
What do you dislike?
It would be useful if Google E-commerce Analytics were a simple plug-and-play integration; as it was, this integration required some customization. Sometimes I've needed to hunt for awhile to find a feature buried in the system settings, but with such a complex product I'm not sure how valid a complaint that is.
I would also appreciate better documentation and support of the K# syntax used in macros - I'd like to use these features more than I currently am.
Recommendations to others considering the product
I would recommend thoroughly documenting the features your implementation will need, to determine which can be handled by off-the-shelf features, and which will require customization.
What business problems are you solving with the product? What benefits have you realized?
We need a CMS that can serve customers at several levels: as both an E-commerce site for merchandise products, with all of the features one would associate with a modern online store, but also as a platform to support a longer, "softer" sales cycle for our curriculum products. Kentico provides decent tools to support both of these levels of sales support.