Printed Invoice History
The Zoho Invoice summary screen is lacking with regards to printing and email status support. I can't be the only business who needs to quickly see when invoices were last printed, emailed or snail mailed (whichever was most recently done). Something like "1st overdue reminder printed by user ABC at 10:12 on 20th Sep 2010" would be fantastic.
This feature is would make Zoho Invoice 10 times more usable for me.