I got myself the Japanese version of the game and it's just more of the same great 2D fighting from the first game, but some changes made to the game mechanics, new moves for the cast of the first game and of course new characters. New characters being Hazama, Tsubaki, Mu 12, Trinity the Platinum, Valkenhayn and Makoto. I wouldn't really call Lambda a new character since she is only really a colour palette change of V-13. V-13 is still in the game, but only as the unlimted version of Lambda.
There are a few new modes including legion, tutorial and challenge modes. Legion is kinda boring but the tutorial and challenge modes are great. Challenge is basically just like training except it gives you 10 levels of combos to learn for each character. It's a great way to come to grips with the new characters and the changes made to the cast of the first game. Tutorial mode basically just shows you all the changes made to this game so it's a good idea to make sure you watch this first.
The new characters are great, all very unique in their own ways just what you'd expect from Blazblue. Although I am yet to see Trinity the Platinum and Valkenhayn, as they will be DLC and only Makoto has been released as of yet on the PSN. There is quite alot of DLC too. Not only characters but even the specific character announcers, for example having Toakaka's voice actor saying, "The wheel of fate is turning" at the start of the rounds.
However hopefully the European version will come with all the DLC on the game like it did with Calamity Trigger so you won't have to pay for it. Fingers crossed!