I like how easy it is to customize our account with custom fields for marketing and reporting purposes. The UI/UX could be better at this stage - some functionality are not intuitive enough and we have to dig through options menus / sub-menus to find what we want (for example, there's no way to select multiple emails in one go). We use Tapleytics as an open source toolset within Salesforce Marketing Cloud. This helps give us flexibility when creating automated workflows such as Welcome emails or Lead Nurture sequences via AIF360 Workflow Builder.