I had read IGN's review and it didn't explain anything. If anything it made me confused but in the comments someone recommended the NintendoLife review
and this one gives a great idea of what to expect of the game, the features and more. Even digging for information for some months now there was a lot of stuff I just found out about SMTIV by reading this review.
One thing I found out which sound great is the "app points" you gain, but now it seems you can use them in much more ways like, upgraded space for more demons or skills, negotiating tools, experience boosters, and hacks to lower MP costs, raise the level cap for demon fusion, regenerate HP or MP as you walk.