They have been very helpful with our email campaigns, they know what works! We've had them create emails for us that were tailored to specific customers' behaviour - this has increased engagement rates by up to 30% in some cases!! The communication is great too as I get regular updates about their progress which keeps me informed when new features or changes occur within my account area of Mailchimp (which we use). Nothing really at all so far but it's only early days yet :) It would be good if there was more integration between different platforms such as Salesforce/Hubspot etc though you can't always do everything yourself without hiring additional help from time to time. If your looking into building an eCommerce website then this could definitely save money down the line since these guys will take care of much of the work needed upfront whilst still making sure things run smoothly once launched online.