Personally, I've played (so far!) without honour. In all my games on Bay 12, I have been acting on expediency -- if I speak the truth to you, it is because I believe (ideally) you knowing it benefits me somehow, if not the both of us. Conversely, I might lie to you if I thought it would benefit me in some way as to outweigh the lie being caught. The question I would suggest to ask in any dealing: what does it benefit the other?
Besides expediency and Machiavellian self-interest, I've also tried to play with some roleplaying weight. My characters try to be themselves, they try to represent -- in 401, I am (or was) a demon from the underworld, sent to claim the world for death. Would you strike a deal with something like that? I know my neighbours did so only reluctantly, out of necessity. In 402, I play a group of people acting as though they represented the will of the people, as though they were the revolutionary posse they claim they are. In truth, they are power-hungry old men, who have now found immortality and more. They lie through their teeth if they think it can get them anything. Sure, there are a few true souls left in there, and so they might have a say sometimes. But who is Strangefather? Hah! Perhaps he is trustworthy.
I do worry. When I'm not sure that the other person is aware of the game I play, I do feel guilty. If the other person thinks that my actions are representative of me as a real, fleshy person, and I then act as if I was a lying vampire... well. It does hurt. So here is my warning: I'm playing a game.