I did Fall 2005 in Merchandise and was placed in Toontown. I had an absolute blast there! The managers are awesome and really understanding, you are able to make lots of magical moments for people, and it was just a fun enviroment to work at. Only downfall was Potato Mountain! Boy, was it frustrating to clean!
I also worked at Pirates for two weeks, the costumes are not comfortable and did not fit me well at all. In fact I was told my first day there that if I wanted to come back I could wear the Adventureland costume. That costume is much more comfortable. Pirates was fun to work at but you just listen to the same song over and over again (in Toontown we could basically play any Disney music).
I was also deployed to Strollers in Magic Kingdom, which let me tell you, for the week that I was there I thought I lost 10 lbs!!! It is definitely difficult to set them up, clean them, put them out (morning shift) then clean them, stack them (closing shift). The upside to this was I worked there on the first Mickey's Not So Scary Halloween Party and was able to get a really great view of the fireworks that surrounded the park.
Honestly, just go down with an open mind and you will be fine. The program is really what YOU make of it. I know some people end up hating it, but then you have the people who love it. If you go down expecting to be put in your favorite store, attraction, resort, then you may end up being disappointed and not having as good of a time. With all the thousands of places for you to be put its kind of hard to say where you will end up.
So good luck, keep an open mind, and just have a great time!