Bingowings said:

Lando was looking out for the entire population of Cloud City.

The residents of Cloud City aren't really presented to us as a character in the film.....the way that the Ewoks ARE presented to us in ROTJ....I've always felt that Lando was much more selfish, looking out for his own interests. He sells out his friends to protect his own ass (not that he has much of a chance against Vader)....and then sets about making it right once he can do something about it. The film's focus is not with the residents of Cloud City.....but with Han & Co. and Luke. Lando betrays them, then helps them. He goes from bad (even if forced to be bad by circumstances out of his control) to good.