This is definitely an area where they could improve the online experience.

Last week I was in a bit of rush when leaving my hotel and didn't go to the front desk, just walked straight to the subway. There was no way for me to retrieve the folio/bill/receipt online so the next day I had to call the front desk, ask them to send a receipt to my e-mail and wait. And wait. And wait. About four hours later an e-mail showed up in my inbox.

Allowing me to go online and see the folio per past stay would be fantastic.