We run a certain proprietry service on many of our servers. The database it uses is locked whilst the service is running and standard backups miss them.
The vendor's official position is that backups are pointless because their service is so good it can never go down or experience corruption, which we all know is kind of silly.
To cut a long story short, AOFO is a life saver in this situation. It should be mentioned AOFO isn't supported by anyone in this configuration- the service vendor is useless, and Symantec can't be expected to support backups of a product they've never seen.
We have however done multiple DR tests and satisfied ourselves that it _does_ work. If you ever find yourself in this position, do yourself a favour and purchase AOFO.
There is a tricky situation of course, where servers skip files in the printer spool and similar, and the "your backup had exceptions" leaves you wondering whether you should be doing better, when you're in fact doing fine.