Me too - it seems like there is no "Email - Performance Details" report type available. In fact this morning I created a new Email Performance report in the Analytics tab just in case I misunderstood and this new feature was inside of it, but the report displays an "Error running report" message, but an older version of the report with the same Setup and Smart List works fine :0(
TJ, the help article says it will be rolled out starting in April and April is almost over and this feature is now listed in the What's New page of Marketo, but the help article it links to is cryptic at best. That's why we are a bit confused about it. Does "rolling out in phases" mean that its functionality is going to be be rolled out in pieces or does it mean that some users will get it before others? If in its functionality will be released in pieces, can you describe what those pieces will be and when they will come out? Will there be a more details added to the help article on this feature? Will you also migrate our 2013 email data as well?