He’s not even close to my favorite church leader, but he did a lot of things in his tenure, giving him lots of chances to do good or ill.
Basically, he was very “liberal” in his social morality and very “conservative” in his personal morality. (Quotes used, here, to show popular perception without getting into a separate discussion of what the words should mean.) Of course, this means that one’s views of those aspects of morality will color one’s views of how good or bad he was.
He really did have a lot to do with the destruction of the Iron Curtain and the end of Soviet hegemony in Eastern Europe. His role has been overplayed by some, just as Reagan’s has been overplayed by some, but he clearly stood up and condemned the Soviet practices and, coming from Poland, created a rallying figure who inspired the uprisings by Solidarity and other groups that drove the earliest wedges under the wall.
He also went out of his way to attempt to atone for or seek forgiveness for earlier actions by the Roman Catholic Church, insisting on a re-examination of the trial of Galileo after which the church declared that it had erred in the trial, going to Greece (in the face of harsh criticism) and asking forgiveness for the role that the papacy and the Western church played in fomenting and perpetuating the schism between the Catholic and Orthodox groups, and offering similar official apologies for other acts.
His pronouncements against corporate greed and the dehumanization of workers have been consistent througout his papacy.
And he put himself “on the road” so that people throughout the world could meet him. (This was not simple PR, although I’m sure PR played a role–he often got off the plane criticizing the host government for various actions it was perpetuating against the people of that nation.)
He also spoke out quite forcefully against political involvement by priests, eventually ordering any priest who was in a government office to resign (either the office or the priesthood).
I have a number of issues with which I disagree with him, but they are philosophical differences in which he consistently held to his position. The one area in which I found myself actually losing respect for him was in the blatant hypocrisy of the disparate treatment of the schismatic Cardinal LeFebvre contrasted against the treatment of the proponents of Liberation Theology. In both cases the Vatican’s official position was closer to its core teaching than either of the other groups, but the Liberation Theologians (who wanted to stay within the church) were chastised and silenced while LeFebvre’s group was coddled and encouraged until it actively broke with the church. (And, obviously, this sort of in-house feud is going to be of less interest to people outside the church.)