I like Oguri Shun in the begining of the show... but as the show goes on, just didn't like him that much. Yes, it is difficult to portray Hanazawa Rui, and Oguri Shun doesn't really give me the Rui feel in the drama.
As for MatsuJun, other than his minor shortcomings (height, don't look that good in curly hair), he's a pretty decent actor. I particularly like him in the last few episodes when he was rooting for Makino.