Tl;dr: Battery-backing your solar installation gives you easy, clean outage resilience that is hard to achieve any other way. If you live in a particularly outage-prone area, it may be very useful to you. As with rooftop solar, it takes a few months longer than it should to get started, but once started it’s pretty reliable.
Did you end up financing, or just cutting a check? Also curious about the capacity--how long can your home run on battery if the power goes out?