I like that it's easy for me as an agency owner/manager of our email program, to keep track of all my client data with one dashboard! Some minor issues we've run into are keeping up-to date across multiple clients (we have about 150) but nothing major or hard core - just some small things here & there. Keep your eye out when you're testing new campaigns because sometimes they will not update correctly so be sure to double check what is being sent from time to time.- Keeping everything organized at once instead of having lots of individual dashboards would make this process easier if more people were using them.- Having access to analytics reports within each account makes managing accounts much faster than trying to go through different tools individually to get info together.- The integration between MailChimp and Hubspot was confusing initially until someone explained how both pieces fit together well enough to work seamlessly without any problems down the road.