I really like the postcard feature, it fits very well with this kind of exploration heavy game. It also is obviously designed to encourage players to share nice screenshots that just happen to have the Submerged logo emblazoned on the bottom right hand corner. I wonder how frequently it will be used, I hope at least it will be used by more skilled hands than mine.
I did learn to appreciate the unlocked camera that it provides, later on when I was focused in collecting more of the secrets this game hides I used it to get a better viewing angle around corners and over ledges to try to find the right paths. An unlocked camera can be a very useful tool.