Waitlists are different for each school. You might want to contact the school to find out:
1. Where you are on the list
2. How many people are on the list
3. What there protocol for pulling people on the list is (i.e. do they pull in order, look for matched candidates to those they lose, etc.)
4. How fast their list has moved in past years
Other than that, it's pretty much true, they're long, they move slow, but your chances are best after May 15.