I like their customer support, always willing to help you out with any questions or concerns that arise during your campaign development process! They are very easy going people who do what they say when it comes time for implementation of our campaigns into production environments (which is often delayed). Sometimes we have issues getting certain elements from them in terms of updates/changes which can be frustrating at times but overall great experience working together so far!! The biggest challenge has been trying not get too attached as this relationship will likely end once my project ends here - however there isn't anything specifically about click engine's services themselves where i feel negatively towards other than just how long things take sometimes due to delays between approval stages etc., especially since all work gets done by top notch individuals within each department making up CEM staff :).