every time this topic comes up, I always say the same thing - better to have someone who votes with us 60 to 70% of the time, than someone who votes with us 0% of the time.
Honestly, Brown has kept to his word - he said he would vote as he feels is best for the state, not lockstep with any party - and he has done that. Granted, I don't always agree with his decisions, but agreeing with him most of the time is far better than none of the time.