I've been using Wind Internet (the 4G box) for over a year and overall it's good, for DR: the speed tends to be close to the contract rate, with some occasional slowdowns and outages (mostly at night). I like that I am not tied down to a specific place and can just take the box with me and go, and that there is no bandwidth limit so you can transfer an order of magnitude more data than what Orange or Claro wireless (3G) options allow.
What I have is Surf-I. If you end up trying Wind, make sure to check their 4G coverage, it's currently in major cities only - i.e. not in places like Cabarete, Jarabacoa. They give you 3 days to check that your coverage is good.