Okay... I am already a big fan of TTGL, and thus I was drawn out of curiosity to this manga. I must say, though, that THIS is even better than the source material. Then again, I am a fan of many anime and manga that are based around high schools, so this seemed like a fusion of two great tastes. Anyways, the characters are awesome beyond their normal means, and to see Kamina go the entire story WITHOUT dying heroically is a miracle, despite him stepping out of the way to allow Simon to rise to glory. I also like how Nia and him (Kamina) sharea similar taste in magazine...and how Nia declares that she was Simon's wife after just one 'Gattai'.
However, what REALLY made her character was that her other personality was not as cold-hearted overall unlike its TTGL equivalent, and it reminds me more of a YM-esque Dream Demon or a YGO-esque Yami form than the Anti-Spiral messenger that announced doomsday. In fact, because of that, the ending is a lot more satisfying than the source material.
In conclusion, if you liked the characters of TTGL, and are a big anime fan like myself, check this nice piece of comical genius out.