I think it's fun and useful to boldly look for what I don't know I don't know. The good news is that I'll never run out of it.
One thing you might not know you don't know is that how you look and sound to others reveals something about you that could be a clue to expansion. For instance, in a recording of your voice you might hear timidity or nasality or brusqueness that you aren't able to hear through the bones in your head. And a photograph can reveal to you a tendency in a relationship that you weren't aware of, or show you something about your fitness or vitality that you haven't been alert to from the inside.
So, I don't think the value is so much about in-order-to's (like correcting weaknesses, etc.) but rather, expanded awareness (that might lead you to inspired action, and might not.)