In my humble opinion, Harvard SSP is overpriced and mediocre.
Contrary to popular belief, the program does not help you get into Harvard; additionally, a number of colleges regard these "expensive programs" in low esteem, considering that they discriminate against low-income students. The class sizes are generally large, but that may only apply to popular general classes -- if you choose a more specialized and/or higher level class, you'll probably have a smaller class-size and therefore be able to form a closer relationship with the teacher (I did not have this privilege, as I chose a more general class.)
In summary, it is my understanding that one of the primary motivations for Harvard SSP is to make money. Their gross-profit on this program is probably significant, and they generally feed from rich students. However, take my words sparingly -- depending on your luck, this could be a gross generalization. As to whether you should skip your finals to attend, I would vote against doing so.