I am not an expert on the Cuban economy or Cuban politics, but from the little I have read, faced with the US embargo and it's geographical location, Cuba seems to have done surprisingly ok.
That is entirely accurate, but doing "surprisingly okay" for their situation isn't exactly what I would call good. I watched a documentary on modern Cuba a year or two ago and it was very poor. Crumbling tenements built 30 years ago, junker American cars from the 50s still in use today, nobody has enough food, the health system is good in theory, etc. All in the shadow of the booming tourism industry. They could be doing a lot better if restrictions on private enterprise were lighter and the embargo was over, the only people hurt by the embargo are the Cuban people.
I have a guy I work with that just went to Cuba. He said it's extremely poor. He was amazed by how much you could get with just a few dollars. His family is cuban and they all resent the shambles that the country is in. While guybrush is right that it is amazing that they've done as well as they have in spite of the US embargo, imagine what a better quality of life they would have if the Castros stepped aside.