Before the revolution, Cuba was a client state of the US, with an economy based on tourist dollars and export agriculture. All the wealth was concentrated in a few hands and, like other countries in the region, the majority of the population was very poor and largely illiterate. When land and other resources were nationalized, the wealthy were (naturally) disenfranchised. Education and health care, rather than being privileges of the elite, were made available to everyone. Today Cuba has almost universal literacy and more doctors per capita than the US. (Read more here.)
These issues may not seem like such a big deal to people comfortably established in (over)developed countries. To put those achievements in perspective, you have to compare Cuba to other countries in the region, like Haiti. There, illiteracy handicaps 55% of the population, and many lives are lost to diseases and infections that are preventable or can be easily and inexpensively treated elsewhere.
A lot has been written about Cuba's environmental initiatives, particularly since the collapse of the Soviet Union and the US imposed trade embargo that left Cuba with little or no access to fuel and other goods. Hundreds of thousands of bicycles were imported (from China) to help solve the transportation crisis when the flow of gasoline was cut off. With petro-chemical fertilizers and pesticides no longer available, organic urban and small-scale agriculture became the norm, enabling Cuba to feed its people despite predictions that the starving masses would overthrow Castro and beg for foreign aid to save them. And most recently, Castro has questioned the techno-fix of transforming food crops into bio-fuels to replace a dwindling global supply of oil. If the policy changes that the US hopes for don't materialize, Cuba is on its way to developing a local, sustainable economy.
The Cuban government has not been perfect. There are rumors of political prisoners and of the silencing of political dissent. But lets not hold Castro to a higher standard than we do with, say, George W. Bush. Remember that no country imprisons a higher percentage of its population than the US. And political dissent here is both actively repressed (ask any activist - or bystander - arrested at a New York demonstration during the Giuliani years) and misrepresented or ignored in the press. If a massive demonstration is happening and the mainstream media only says to avoid midtown because of traffic congestion - dissent is successfully marginalized.
Cuba, meanwhile, offers living proof that the US empire can be resisted, that there are alternatives to the corporate-controlled, neo-liberal economic model. It is a beacon to other countries in the region, and to oppressed people around the world.