We're in the early stages of evaluating dedicated survey platforms that will integrate with Marketo. I know of one that's been promoted here in the community - 123FormBuilder - but the integration requires you to create custom fields in Marketo to capture the survey results within each lead record. That's specifically what we want to avoid. Otherwise, I can see our custom fields getting out of control. Rather, I'd rather have the data stay on the survey platform and use a unique identifier (email address, MarketoID) to connect the two sets of data. If anyone has recommendations, please share them here!