From desktop SAGE reporting we have lost the ability to run a debtors report for invoices to a particular date, but allowing payments/allocations to a later date. This is a key audit report as it allows us to quickly show how many of invoices to the year-end were outstanding at the year-end but which have now been settled. All the other online accounting packages that I use have this facility.
It's also important for allowing statements to be sent to customers showing only invoices to the previous month-end, but allowing any subsequent payments to be reflected. At the moment either all the invoicing has to be synced to the date of the statement run, or I send statements to customers showing invoices they have already paid.