I'm also waiting on the I-20 form. I don't really know a lot about the visa restrictions but I was hoping to get there in early/mid August. I have some friends in Boston who are going to help me out. If I have to wait until mid August I might stop over in London for a couple of weeks.
I'm glad to hear about the dorm accommodation. Some people have told me that grad accommodation is a really good environment, but I'm sure off campus is fine because Boston looks like such a student friendly city. Plus, I want bring my cat. I'm going to try and find something on the red train line. I went to a conference at Tufts last year and I liked the area around Davis/Somerville. Sounds like we'll all be hitting the local IKEA at the same time!