I'm not a fan. Don't dislike him either. But I always have the feel he's been given his success, didn't earn it - not more than another superstar I mean, they all work hard, and I know Sheamus payed his dues in Britain and developmental.
But he arrived on the main roster and was having a WWE title match a half year later. All his matches were with guys like Cena, Orton, HHH.. and the matches with Cena and Orton - apart from retiring Jamie Noble - are the only ones I can remember. I've been reading his wiki to check some things for this post, and I really can't remember any match that wasn't a) a gimmick match like MITB or b) a match against a legit main eventer.
So, to summerize: (in my opinion) he's a decent star, he had a good heel run and was pretty over with the kids as face, but I can't remember him ever doing something really great and he could be off tv for two years and I would'nt miss him.