It did change. The idea is more of a shonen plot, but the art style and even the mannerisms of the character have changed somewhat to be more feminine. But I think it's because the mangaka is actually a woman and perhaps naturally shojo elements appeal to her more and she can't keep a consistent shonen story going without swaying into shojo somewhat. Like the Kanda story and all and his relationship with Alma was a long "romantic" drag that could be expected in a shojo.
would you consider it a change for better or worse? I really want to read d gray man, but if it just gets crappy halfway in then theres really no point to it. Id like to know what you think about the series as a whole