Communism is a utopian philosophy, so in theory it is really quite good. The ultimate goal of communism is to have a society where all resources are shared equally based on need, property is all owned collectively, there is no state, and work is done based on personal desire rather than economic need. To read Marx and Engels it is difficult to imagine a person that would not want to live in the world they describe as the end Communist state.
It seems that in reality the problem with Communism is that in order to get to the utopic end we must first pass through a time where the state has incredible authority and control (in theory this is necessary in order to set the foundation for the dissolution of private property and the state itself). So far, no state has actually acheived Marx's described communism because no government has been able or willing to give up that control and power that is required during the interloping period; subsequently, rather than having ever seen a communist society we have only witnessed socialist authoritarian regimes that pass themselves off as communist, which in practice seems to have been an undesirable state of affairs for many.
