I originally thought killing off Han was a good idea, but the more I think about it, the harder it seems to do.

If Han dies early in the movie while being rescued, it adds a lot of gloom to what is supposed to be that last of the lighthearted adventures of Luke et al. Also, there likely wouldn't be any glory in his death. A beloved character like Han deserves to not go out like a punk. In the end, his story still seems like a dead end. People say his death would add more tension to the movie since it sets the tone that any other of the main characters could die as well. I disagree. I think it accomplishes the opposite, since more than one main character dying is very unlikely. Yoda's death is already sufficient to set this tone.

If Han dies late in the movie, it will overshadow Vader's death, which should be one of the most important moments of the Saga. We would feel worse for Han, who we've seen over 3 movies grow into a new person, rather than Anakin, who's changed in only over a few minutes.

That leaves only the middle of the movie. It could be done, but only very carefully. Too shallow, and his death is a massive let down. Too dramatic, and it overshadows the upcoming action. I like the idea that he should sacrifice himself, but how it should be done is very non-obvious.