I'm half-way through  a 10-day trip to the Dominican Republic. Here's a random collection of things that stood out to me:

• Relations with Haiti. The DR shares a border with Haiti. The DR is the richer country, with a GDP per capita ~6x greater than Haiti. Relations with Haiti are sometimes tense; there are lots of Haitians who illegally cross into the DR in search of better job opportunities. Many work in labour intensive jobs like sugarcane fields and are paid very little.
• The Parsley Massacre. Around 20,000 Haitians were killed in 1937 by the Dominican military due to concerns over illegal immigration. The way soldiers determined if someone was Haitian or not was to ask them to pronounce the Spanish word for parsley (perejil). Haitians speak French and could not pronounce it the same way as Spanish speakers do.
• Roads. I had heard that some of the roads were in really bad shape, but never saw this myself. Every road I saw was really nice, up to North American standards. Even the roads in small towns like Boca de Yuma were really nice.
• Economy. Quite diverse and not solely dependent on tourism. Tourism is less than 10% of GDP ($7.4B). Agriculture is a big chunk of the economy: primarily sugarcane, tobacco, tropical fruit. There is also mining of nickel, gold, and silver.
• Tropical fruit. Lots of tropical fruit grows here and it's all delicious. I recommend trying at least pineapples and mangoes. The mangoes here were able to rival Indian mangoes in their sweetness, which is very unusual; most mangoes grown outside India/Pakistan are terrible.
• Currency. The official currency is Dominican Pesos (DOP), but US dollars are accepted in most places.