Ability to filter on time tracking related fields (Original estimate, Time Spent and Estimated time remaining).
It would be possible to specify a range.
Examples
From : 1
To : 10
From : Empty
To : 10
would mean les than or equal to 10
From : 3
To : 10
would mean between 3 and 10
FROM: 1h
TO: 1d
or
FROM: 3d
TO: (null)