I have the app and absolutely love it. I do not find it difficult to use at all. In fact I can often find things in it faster then I could by looking it up in the phe book. The best part about it is that I carry my phone with me all the time (I use the iPhone) and so I don't have to ever worry about not having a ready reference when I need it. Plus I like that I can input the foods and the program adds it all up for me – I don't have to put too much thought into it.
My oldest daughter has an ipod and she has the app as well, and I don't think she finds it too difficult to use either, and my 12 yr old has looked stuff up on it without difficulty too. There is a search feature that I like and you can also add foods if you find stuff that isn't in there. There is also a section for adding recipes which I like but don't use often
The only hang up is if you count exchanges (like my 12 yr old is just starting to do) then you can't use the app.