that sucks about the housing, but i am fairly certain that there is guaranteed housing in harkness for all incoming students, regardless of how late you got in from the wait list. I applied for housing a couple weeks ago (for harkness), and am waiting to hear back to see where I got in. Dr. Silverman said that housing was guaranteed, though (and I think about 50% of the class stays in the dorms).
My personal reasons for choosing Harkness over my own place?
Location (I can walk to class and not drive anywhere), my food (and other worries) during the week is taken care of, and I can meet people in a city and school where I don't know many people. I also like the idea of not having to clean my bathroom and kitchen, at least for a year... though I can't foresee myself in the dorms from MSII on. Besides, I figured, I would probably never live in dorms again after this, so why not?
It should be a good experience.
If you're looking for a more quiet lifestyle, I think there are several options within Harkness... all the rooms are, of course, singles, and the difference between an extra large room and a large room is only about $300 per year (comes up to about $667/month for XL). You can also get quieter rooms (well, according to some older MS1s) and they do ask you questions on the housing sheet as to what kind of living environment you prefer.