A fascinating place to visit, Cuba appeals in many ways. For those wanting a tropical beach holiday, Cuba has them in spades from all inclusive resorts to hidden beaches. Hiking, biking and other outdoor activities are on the cards. Colonial architecture, in various states of collapse, dominates many of the cities. Music abounds and classic American cars still dominate the roads.
There are a few downsides to the place, however. Tourists must take private transport or use the Viazul bus company, which is more expensive and less convenient in that there are fewer departures and fewer destinations than the other local companies. Food is decent but very limited in variety, so after a while you start to crave variety (rice, beans and chicken feature in most meals). Museums tend to have great potential, in that they have good raw material, but the curating is terrible; there is no organisation or explanations of the bigger picture of things, they're almost always just a collection of bits and pieces - fine if you a) speak Spanish and b) already understand all the relevant history, but otherwise it's very limited.
My recommendation is that you spend two to three weeks, focusing on Havana, Vinales and Baracoa, adding some time at a beach somewhere and getting some hiking done in either Vinales or Baracoa. The rest of the country is interesting but lacks variety; one city full of attractive colonial architecture is much like another and that's all a lot of the places have going for them.