K2 Store is an easy to use, self-explanatory, and intuitive cart extension using K2 items as products. If you are looking for an uncomplicated extension that enables a cart on your site, this is it. I’m currently using it on three production sites and will continue to use it as the extension of choice for such solutions.
What really makes this extension go far beyond great and excellent, is the level of support and responsiveness from the developer. The support I've received goes well beyond what should and could be expected.