Junichi Masuda has been more active lately revealing details about the current 5th generation games Pokémon Black and White on his GameFreak Director's Columns and his recently announced Twitter feed. Below is some of the information he revealed about N and Ghetsis.

Ghetsis

Ghetsis is the one of the Seven Sages and is part of Team Plasma. His name is based off a G/C sharp Tritone, a musical interval that spans three whole tones. The musical note G, pronounce “Ghe” in German (written “G”) and the musical note C sharp, pronounce “tsis” in German (written “Cis”) is a tricode chord and the basis of Ghetsis name.

N

He is the leader of Team Plasma, the main antagonist in Pokémon Black and White and was raised by Ghetsis. Below are the points in order that Mr. Masuda posted on the Japanese blog portion of the Director's Columns.

• N's name is actually Natural Harmonia Gropius (ナチュラル・ハルモニア・グロピウス)
• The "N" part of his name comes from the natural number mathematical term.
• N has a IQ higher than most humans.
• He is a genius at math
• He is quick-witted and has intense emotional changes.
• N can perceive a person's past and future.
• N's true parents are unknown but it is rumored that he was born by Pokémon.
• He loves Pokémon and avoids humans.
• N regards himself as being perfect.
• N always puts Pokémon first.
• As N is feared by humans, his connection is strong with Pokémon.

Sources: http://www.gamefreak.co.jp/blog/dir_english/?p=455 and http://www.gamefreak.co.jp/blog/dir/?p=539

It would have been great if they had explained more about N in the game themselves, rather than have to reveal some stuff in a blog post. A bit like the books(?) in the 'mansion', in the original games, which talked about Jungle X.
Black and White really underwent a great deal of improvement in the plot department, but I still believe they could have done even better.

I sure hope Pokémon Grey (if they ever decide to make it) will shed some more light on N and Team Plasma's story.

I'm actually glad that we get an official source like Mr. Masuda revealing this information himself as its considered canon when a person with his position and knowledge disseminates the information regardless if its posted on an official blog or in a book. It gives us more information about N which is good because like you said there still isn't too much known about him.