From the beginning of Battlestar (the mini series), Baltar has always been my favorite. James Callis is exceptionally talented and portrays this sniveling weasel (Baltar) beautifully. In a story where the survival of the human race seems to often rest upon the shoulders and be dictated by the decisions and actions of just one person, Gaias has demonstrated that in his mind, his life is far more important than ANYONE else's. His determination for self-preservation is remarkable. The human want and need to survive is generally strong, but with him it is the number one most important thing. Even the most selfish of people can generally pertain to self-sacrifice for the greater good (survival of everyone else, survival of the human race). Not Gaias. His allegiance is to Gaias and Gaias alone. Nevertheless, he is a remarkable character, he displays the cowardice that so many have but managed to hide, or are not tested to show. He is the ultimate definition of survival of the fittest and looking out for number one.
Not only did Gaias manage to help bring about the destruction of Caprica and the 12 colonies, but he neglected to inform anyone of the Cylons he knew of (Sharon and Six/Caprica). Then he gave a nuclear bomb to a six, the same bomb that eventually led the Cylons to New Caprica. To top it off he is helping them to find Earth. (This is how far I have got so far - mid-season three) Regardless, it is still true to say that the interests of the Cylons and humans are still beneath his own. He'll help them find Earth because he wants to find Earth and because his life is at stake!.
On another note, his delusional apparition of Six has been very comical and entertaining throughout. It is sheer brilliance not just that she is a fantasy of a womanizer, but also that he appears to interact with her in a way that leaves the rest of the characters believing him to be odd, maybe even insane. Very funny indeed.
He's a coward, funny, quirky, smart & stupid and most of all he's selfish- he's human. Perhaps not the best example of humanity but human nonetheless.
I don't think anyone else could have portrayed this character better. Well done James!