While some of the existing charts/reports on the dashboard are useful, I would really like to know about delivery rates / failures by the domain we are sending to (or ideally ESP... i.e. hotmail/msn centurytel/centurylink/embarmail).

I usually end up hearing about a block or other delivery issue from our users. Short of pulling data over the API and parsing it myself I know of no way to accomplish monitoring this currently.