The problem with the true Calvinist position on God is that it makes God into an angry kid who smashes sand castles for no real good reason. God randomly forces some to be saved and others not to be saved because that is how He feels. If your one of the lucky ones, you may be chosen by God to be saved.
The problem with Calvinism is that it seeks to take a lack of responsibility for one's own choice in choosing God and His good ways. Things like: "...Well done, good and faithful servant; thou hast been faithful over a few things..." (Matthew 25:23) is non-sensical in the Calvinistic world. So a verse like this (among many) has to be changed to fit Calvinism (Instead of a person just reading and believing the Bible normally).
The problem with Open Theism (Which is the other opposite wrong extreme) is that the individual is seeking to make God into a man so that they can understand God and the world He made better. Open Theism is one wrong extreme end of the spectrum while Calvinism is the other side of the wrong extreme end of the spectrum.