I used Lose It! for a while. It was very similar to what you're describing.

In my experience, the hard part is not having an app, but actually bothering to log everything you eat. It's easy if you only eat prepackaged foods. It's worse if you eat anything that's not prepackaged, because you have to weigh everything. (If you want a PB sandwich, you weigh the bread, then you put peanut butter on it, then you weigh it again, then you write down / input everything into the app.) It's worst if you try to cook at home, because then you have to go into full calculations figuring out calories in all the ingredients, weighing the final product, etc. Huge hassle. And you can't drink alcohol at all because no one knows how many calories you have in there. (You can make educated guesses - one bottle of domestic swill like Budweiser is 100, Hefe or IPA could be 150, higher ABV craft beer could go over 200), but it's very approximate. Compared to that, it does not really make much difference whether I use an app or a pen and paper. I don't mind spending 5-10 minutes in the evening once every few days tabulating calories.