We've used it for some time. As stated above does nothing for packages, including Priority Mail. A step forward for USPS. We use similar notification systems for UPS as well.
Now, provide you information. Perhaps tells you whether it's worth the effort to check your mail. One note is that it's not available for any mailbox service.
Good for most people and good to help detect theft from mailboxes. Still doesn't do anything like St. Brendan's and other travel services.
We don't use St. Brendan's but basically use the same functionality at home when traveling. We have someone pick up our mail and they scan envelopes like St. Brendan's, scan documents, set aside originals we want saved or sent to us. We keep virtually no hard copies, only those forms that must be filled out. We also do the same in our business. Physical filing cabinets are primarily things of the past for us.