I was originally hesitant of purchasing this game because I already played the original on the DS. I have gotten about 2/3s through the original game and haven't beaten it.
I really love the shin megami tensei universe and like turn based strategy games. If you like either, you will really like this game. The fact that there is an actual story, a good story, makes this game really great.
If you haven't played this game before, it is a must buy. If you have and haven't beaten the original (the one released on the DS), then I would suggest picking it up.
There are a few striking upgrades to this game to the DS version which makes it worth buying;
- Voice Acting for most of the main dialog(quality voice acting, very well done).
- Graphical Upscale for the 3DS (Game Sprites have increased resolution, DS games look pretty terrible on the 3DS).
- Additional Chapter at the end of the game(I don't know much about it, I haven't beaten this game yet on either platforms).
There is one big con however that I see, but it doesn't really affect me.
There is no 3D beyond the intro movie. This is a bit of a miss opportunity considering that Shin Megami Tensei games are usually battled in first person view. This means that they could have capitalized on that fact and made the first person view use the 3D function and make the battles more 3D.
I can not see 3D due to eye problems so I don't even have any idea what 3D looks like, but I imagine that it is probably cool to people who can see it.
Bottomline; If you are on the fence about this game and haven't played it or beaten the original yet, get it. The story is compelling and the gameplay is fun.
If you have beaten the original and are thinking buying the game, realize the game is pretty much the same except for the increased resolution on sprites and additional voice acting(which is quite good).