The concept of playing characters once they are dead, if done right, is interesting. I don't think the way Ghostwalk approached things was this right idea, though, so I voted as not liking either - I don't like playing characters after they are dead in the Ghostwalk way. I don't like having a big city of undead, having different types of ghosts, having such a set and unique cosmology, and so on.
The game I like for this is Infernum - where the players essentially play characters in hell. I could very well see starting a game there with the players' dead souls as the PCs, perhaps aided by a trapped mortal or angel, wandering wizard, canniving demon, or so on. Although the cosmology is more specific it is based on Dante's hell so it makes far moer sense for me, and fallen angels, condemned souls etc. make much more intuitive sense.