Library Elf?

Has anyone used Library Elf? Any patron feedback?

This site is supposed to track your library book due dates.
According to their FAQ, here's what they do:

Elf is an Internet-based tool for keeping track of what's due, overdue and ready for pickup. Users can keep track of one or more library accounts in one place and receive reminders (sometimes called pre-overdue or early notification). Reminders are sent when the user wants it -- before items are due (up to seven days advance notice, weekly notice or everyday reminders). For families or anyone who'd like reminders before an item is due (user-selectable number of days notice).

An interesting concept but some might be worried about privacy.
However their site says:

With respect to privacy, is a record (history) of the titles kept?
In general, no histories are kept or recorded. Due to the way RSS works, however, an RSS file is published for users who have chosen to receive RSS feeds. Old or previous RSS files are not kept or retained. It's worth noting, Elf does its checking in real-time and information is based on what is obtained at time of checking (and not stored).

Is Elf affected by the US Patriot Act?
We don't think so. We are based in Vancouver, BC Canada and it's our understanding that the US Patriot Act does not apply here. Furthermore, our privacy policy states that we will not share any information unless ordered to by a government court order (which, in our case, would be the Canadian government).

Elf only does its checking in real-time. This means that no history file is kept of your items out. Due to the nature of RSS, a copy of one's current account status is kept for your RSS feed, but this only if you have opted for RSS feeds.
Library Elf