Some Japanese gamers have managed to get the game early. I've checked the Twitter accounts of these people and also the topics on 2Chan. The response to FFXIII-2 is somewhat negative so far. Below is the general sum up from people who got the game early (somehow) and have played up to 20-40 hours of the game. More reactions should come in when the game actually gets released on December 15.
The most commonly voiced complaints
1. The story is incomprehensible and too convoluted. You need to always access the Datalog to understand what's going on and even the Datalog descriptions are hard to understand.
2. Noel doesn't feel like he belongs in the game. He has been compared to Vaan, but instead of being irrelevant to the story, he has been made forcedly relevant in both cut-scene dialogue and backstory. It makes it seems like the theme of the story is not about Serah finding her sister and more about Noel.
3. The towns are as bad as FFXIII. You can't enter a single house or building and there's hardly any NPCs in the towns that have something interesting and unique to say. Most have basic info on what's going on in the story and where you should go next and others offer basic side-quests. There's no NPCs with their own dreams and ambitions and their own thoughts and feelings. The only NPC who gets these traits is Chocolina.
4. You start getting sick of only having only Serah and Noel in your party after the first 15 hours or so.
5. There are side characters (Snow, Hope) with better development than the side characters in FFXIII (Cid Raines, Rygdea) but they come for only half of each chapter.
6. The graphics have taken a downgrade compared to FFXIII. The quality of textures is not consistent throughout all the locations. The game is inconsistent in visual quality.
7. It's not linear but once again there is only one open area to explore (Archlytte Steppe). All the other maps are interconnected corridors with some big spaces inbetween them.
8. Academia is a deceiving location. Upon arrival, it looks like an epic scale town, but in reality it's only a quarter the size of a town in the first Assassin's Creed. Also, as with the other towns, you can not enter any houses, shops or buildings.
9. The levelling up is worse than the Crystarium in FFXIII. Some of the bonuses are cool but it's based a lot on luck on what options you're given so it can get annoying.
10. Chocobo racing is all automated and really hands-off. You only press a button to boost and that's it. You don't even get to mount the Chocobo you're racing. They feel it would have been more exciting if you saw Noel or Serah mount the Chocobo and race on the track against other rider mounted Chocobos. There should have also been real-time controls like in a racing game (Mario Kart/Ridge Racer).
Some positive thoughts
1. The monsters being in the battle system is actually pretty good. The sheer versatility it brings has improved the battle system even further.
2. The QTEs in the battle system feel like limit breaks in FFVIII and FFX. They are fun and most of them look really epic.
3. Chocobo being able to glide on the field is a good mechanic that makes exploring fun.
4. Soundtrack is one of the best in the entire FF series.
