Would be great to be able to see the performance of individual domain names (ie: hotmail.com,gmail.com, aol.com, etc.) in order to easier identify deliverability issues (with the ability to be able to compare different domain names with each other).
It could eventually be done through custom filters that could be applied on the reports. Advantage of these filters is that it also works on other fields than just the domain names, like: sex, age, etc.