] The knee-jerk reaction to Claudius (for me, at least) is that he's a villain, villain, villain. Well, he is that and more.

] He is courageous
] He is human (his love for Gertrude).
] Regretful.
] Guilty of his actions

Certainly, his general function in the play is as the villian, but I also think it grossly underestimates Shakespeare to assume that he is nothing but a villian. Where's the fun in that? Where's the conflict? That is why I think it is interesting to isolate, if not his "good" points, his rationalizations for acting the way he does.

] While Hamlet ponders whether to kill Claudius while he is in prayer (which would send him to heaven), Claudius acknowledges his insincerity regarding his black deeds. (Act III, Scene 3): [Rising to his feet] "My words fly up, my thoughts remain below.
] Words without thoughts never to heaven go.

I am not sure he is acknowledging any insincerity, just that he can't get his mind off his worldly problems in order to pray. He is very sincere about the deeds he has done - for better or worse - he just can't keep his mind off the worldy issues vexing him. This is one of his defining traits for me - his earth bound nature. He is not a thinker, he is a man of the here and now. But perhaps we are saying the same thing.