St Maarten is worth the walk into town. They have a nice promenade with shaded cafes and bars. We spoke to the owner of the cafe we sat at and he was French and said many of the cafe owners come over from the other side of the island.
In St Thomas they have two cruise docks and we were docked at the one that was a distance from the town. We decided to look at the shops by the dock and go on the tram. We really enjoyed the tram and the view it provided. The owners are renovating the top of the tram area and it was quite nice.
I've been to Nassau six times. The first time, in the early 80s, it was still charming. On trips since, I've found that Atlantis has sucked the life out of the main shopping street and it was dirtier and more rundown on every trip. (And I really don't like Atlantis) However, in the last year, this seems to have turned around. Downtown is being renovated and there are some GREAT shops that go beyond the typical diamond stores. The people you meet are friendly and kind. Do take some time to check out some of the independently owned shops. We were really enjoying our visit until a torrential rain sent us scurrying for cover on the ship.