He's not a bad writer. Not amazing, either. There aren't many really amazing writers in the VN industry to begin with (the only ones I'd call amazing are Romeo and whoever wrote the SR script.) That's not to disparage the medium though, just to say that the writing quality is only part of the reason a given VN might be good. A mediocre script can feel amazing if the music, atmosphere, SFX, etc. are done well. Nasu's writing is like that; the script would be boring if you read it in a book, but it's surprisingly suited to the medium, and the sparing effects that are used in his VN's, especially Tsukihime, are perfectly timed. KGNE is another VN in which, while the script isn't bad, the script isn't the reason the game is good.
Oh wait, I just put way too much thought into responding to a troll.