Heyo! I'll also be starting a Ph.D. at MIT in fall. I decided to enter the lottery for on-campus housing, mainly for convenience. I'm moving cross-country, and I really don't want to go and apartment hunt now. I've lived with my folks throughout college, and commuted to school, so I'm actually looking forward to living on-campus.
The Institute apartments didn't seem too dormlike to me--everyone has their own bedroom (for most buildings), and it doesn't look like there would be any frat party-like gatherings in the apartments (but I'm familiar with neither frat parties nor dorms, so I'm just speculating). What aspects of the MIT apartments reminded you of dorms?
P.S. I'm a "regular" here, but I'm posting under another username for the sake of anonymity.