ChannelAdvisor has been great. We have been with them for about 4 years and have been able to grow our marketplace sales exponentially. We have been extremely happy with the implementation, their suggestions on business rules, and their attention to our account. We have added their managed services component to our account. Through that we have a dedicated manager that we meet weekly with to discuss strategy and changes. They handle everything and it has been a great relationship. I would highly recommend them.