Hmm, I think the story was interesting before the Kayano and current arcs. Now I'm bit put off by the whole thing, but I'm still keeping up if just to see how it all pans out.

I've only watched the Neuro anime, so I'm not sure if the manga is vastly different... But I don't really see much similarities with Assassination Classroom now, except that the sense of humour is similar since it's by the same mangaka.