Hey Rad,
Yes, we are going to write an Invoice report, for the Invoice module. We will probably add the basic filters: date range, client, etc., but we will probably report the fields in a fixed way. There really aren't too many fields as far as the invoice is concerned, so people can always manipulate them in Excel or Numbers if needed. This will be important for tax reporting for many at the end of the year.
Thanks for writing!
Cheers,
Adam.