If a rule or data element fails I would like to see more robust error messaging in the build screen, e.g. which rule or data element failed rather than a generic failed message.
At a minimum, it would be nice to have rule names used in the build error messages instead of the internal rule ID's.
It's coming. We're in the middle of standardizing the way that error messages are created/delivered through the whole system. The messaging for failed builds is included.