Filtering using a Date or DateTime field currently must be selected or set to a specific date. It would be useful to be able to set a relative date and time, i.e. yesterday, last month, last 24 hours; last 28 days etc.
Couple this with the automatic reporting feature would significantly increase the power of the reporting suite. for example, users could set a filter of 'from 20:00 yesterday to 08:00 today', automate it for 0800 every day and receive daily out-of-hours/overnight reporting.