I agree with both of the above posts! I LOVED St. Maarten (actually picked my store's cruise partially because of that port stop!).
My husband and I took a tour of the island, and I took a tour of the island (offered by the RCCL), and really enjoyed the guide and the information.
I didn't like Marigot at all. . . way too expensive
Orient Beach (French side, I believe) is beautiful, as are some of the houses that are on the ocean. I was pretty amazed to find out (from the guide) that these houses are provided for the unemployed citizens of the French side by the French gov't.
It almost made me want to become a French citizen and move to St. Martin!!
the Dutch side. . . The port at Phillipsburg was so clean, and if I remember correctly, you could take a water taxi from the port to the shopping district for $3.00. The main shopping district in Phillipsburg was the cleanest of all the places we visited. I was amazed.
One of the couples at our dinner table took a taxi around the island for the day. Like Billy said, you can find them right after you dock. They arranged the price in advance, and I think that $40 is about what they paid, too.