Even though I really like this interface for adding effects to images, the app is a little lacking in other areas. With other apps you have the option to add frames and labels, which -- while not totally necessary -- can add a little more style to the overall look. The app also doesn't have a lot of textures, but it does have a crumpled paper effect that looks realistic. I imagine as the app evolves we'll see some of these features added, but for now the effect grid is the main thrust of the app.
With that said, Gridditor is a unique way to play with your photos and the self-explanatory nature of the interface will be easy to understand for just about any user. If you like photo effects and want a new way of jazzing up your images, Gridditor is a good choice.