Great suggestion. I had been thinking the same thing and have heard similar requests from coworkers.
And on a similar note I was hoping that another “LIST VIEW” would be provided which would be very similar to the “TIME ENTRIES” tab each project has so that you could view all time entries (accross projects) for a period of time as a list rather than graphically. The TIME ENTRIES tab for projects includes a “Duration” column which may be a help to you even now IF you only need to look at a single project at a time. Certainly though your request is a good one.