I also vote for a roll up feature. My clients only want to see the totals for each project for each day when I submit my timesheet. In my invoices, they want to see only my time for each project during that invoice period.
The current functionality of the reports is fine for timesheets, although it would be a lot easier if there were a "timesheet" view such as:
Sun Mon Tu Wed Th Fr Sat Total
Project 1 0 4 3 5 2 5 0 19
Project 2 0 4 5 3 6 5 0 19
Totals 0 8 8 8 8 8 8
In fact, that would solve both my problems for a weekly view. However, some of my clients want monthly invoices, so it would be nice to have a roll up view for that. Going through and running a report on each project is a pain in the butt. Clearly it's not a deal breaker, as I still use your app.

But it would be really awesome.
Thanks.