Most impressively I have experienced almost zero downtime, less than 1% in errors and glitches with a rapid response to these issue, an excellent customer support structure with round the clock assistance and most of all our sales speak for themselves.
ChannelAdvisor is a powerful tool with almost limitless capabilities when it comes to inventory management. The only downside is that there isn't any WMS so to speak of but it integrates easily. However, we didn't purchase ChannelAdvisor as a WMS.
I would recommend ChannelAdvisor to anyone, a genuinely impressive e-commerce solution.