I've had it for a while, I don't use any of the built in databases, created my own for tracking bookings.
I have requested they provide a means to backup the database to a computer.
You can do that if you purchase the Mac app also, but I have no need for that, so I'm kinda reliant on the iTunes backup which makes me nervous!
I did actually lose the entire database I created and all the data I entered when I first purchased the app after upgrading the phone O/S.
I was really annoyed about that, I'm hoping that problem wont happen again, I have upgraded my phone a few times since then and its not happened since, but the first thing I check now when I do an iPhone update is to check if my Bento data survived.