I vacationed on St. Maarten in March 1995 and stayed at the Royal Islander Club La Plage, a time-share facility on the famous Maho Beach. In other words, my room was offset maybe three hundred meters from the threshold at Princess Juliana International Airport. Few experiences compare to standing in the Caribbean surf as the heavies land mere feet over your head, or being sandblasted by departing aircraft (warning: do not stand on the beach directly behind the outbounds).
Though the traffic was not widely varied, the spotting is excellent. Given the French/Dutch co-administration of the island, the airport had daily flights from both Paris and Amsterdam (at least in 1995 it did). Air France operated a daily B747-200, Corsair had a B747-100, and even Air Liberte and AOM made several charter visits the week I was there with DC-10 aircraft. KLM served the island with a several-times-a-week MD-11, though if I recall correctly the arrival was at night. It's worth noting that Air France's service continued on to Martinique (due to, I suspect, SXM's short runway which prohibits a full-load departure for B747s), so the aircraft turned around quickly, affording the spotter the opportunity to see its departure as well.
As I recall, there were a few other interesting surprises. Lufthansa had a weekly (Saturday) service with an A340, and I even saw a Pluna DC-10 parked on the tarmac. I also saw some Canadian charters, including a Royal Aviation B727-200. Otherwise, traffic consisted of regular MD-80 service from ALM and BWIA, plus feeder traffic with LIAT turboprops. Of course, there was regular U.S. scheduled traffic as well (NW B757-200, AA B757-200 and ATR-42/72, CO B727-200).
I know of nowhere else in the world where you can stand so close to the threshold as a Jumbo trundles mere feet overhead with full flaps and gear dangling. It's perhaps the most impressive spotting experience I've ever had. Though you won't see a large variety of traffic at SXM, the traffic is steady and includes charter types you don't see often in the States (I live in Washington, DC). Throw in a beautiful tropical island and warm tradewinds, and you can't beat St. Maarten as a holiday for the spotting enthusiast.
Let us know if you make a trip there.