The updated and good things about Shin Megami Tensei: Digital Devil Saga 2 as follows...
1. New hexagonal Mantra flow system (MFS). A lot of new skills added for the playable characters. Very flexible to grow your desired skills for each characters, no more follow the Mantra Tree Grid to learn more advance skills. There is a lot of hidden mantra skills too! My advise is to focus on critical skills and plan ahead.
2. In my opinion, half demon transformation form during battle is cool. You will always hit enemies with critical hit and have the opportunity to use some of the demon skills in this form, e.g. devour! However, this transformation is random during battle, only limited demon skills are available, no usage of linkage/ combo skills, and lower accuracy hitting rate! The only good thing I can see which is good about this form is you are stronger than human form.
3. A lot of more useful and new combo/ linkage skills! Some of this very powerful linkage skills are available from the MFS but is too expensive and you need to defeat side-quest bosses to unlock it. Linkage skills are especially useful earlier in the game because higher difficulty level mantra skills are so expensive, most of the time you must/ force to relied on the linkage skills.
4. Voice acting much improved, characters are equipped with more detail facial emotion/ expression. Very good sound effects at the background, it will give you a very realistic feel to the things you touch, etc.! Yeah, there are some very touching CGI near the game end.
5. Very consistent visual outlook and feel, and battle system as compared to DDS1! Not much of relearning needed to play it even if you can't understand Japanese! All you need is play the earlier version SMT series such as Lucifer Call/ Norturne, and SMT: DDS1. Improved CG rendering!
6. You can use Sera and *e**** (spoiler)!

7. New ring and gem attribute system to increase you character's status/ stats attributes. This feature is only available later in the game plot when you are in the tunnel towards the meat factory.
8. Some of the side-quest bosses in the final dungeon is really challenging.
The bad things about Shin Megami Tensei: Digital Devil Saga 2 as follows...
1. Mantra is still very expensive!
2. No pause feature!
3. No soft reset feature!
4. No demon conversation!
5. Omikane is tougher to kill!
6. Final boss is a disappointment! Easier compared to Angel of SMT: DDS1!
7. Can't unlocked the Ceilo shoot-em up game even after completing it!
8. I was not able to unlock Heat and the special power of Gale and Argilla in the final dungeon! grrr.... need to play a second time.