Shame on you Sony!
First off, in and of itself this is not a terrible game however things are what they are and there is a better, more balanced game, which came before. That is: Mod Nation Racers, which as a result significantly lowers the score of this unworthy "sequel".
The racing is completely unbalanced. You may have heard it before but indeed, weapons are too powerful and that combined to extremely aggressive A.I., this "easy go lucky" kart game becomes a significantly aggravating experience.
The editor itself is decent but that's if you manage to figure it out... quite a hefty task at hand indeed. Another huge missed opportunity would be this; with such ridiculously powerful weapons the editor should allow for building weapons and not only tracks! Lastly, how is it that no matter the vehicle parts or type you use THEY ALL DRIVE THE SAME???
Lastly, but very importantly, anyone that looked E3 2012 commercials for this game and owns a 3D TV was completely let down by Sony; THEY DROPPED THE PROMISED 3D SUPPORT! I am sure plenty of people couldn't care less, however for anyone, such as me, that purchased a PS3 system to get more use out of his 3DTV well Sony are outright LIARS! Anyone that doesn't give a damn about 3D, well, good for you.
Overall this game should've been delayed as it REALLY needed more polish to both the karting, track editor and features.
CLOSING THOUGHTS: SHAME ON YOU SONY!