Pro's: great city, pass/fail for the first two years, integrated curriculum, nice hospital (Level 1 Trauma center)
Con's: BU is probably more expensive than SLU, clinical exposure feedback from students has been inconsistent, the medical school is in a somewhat sketchy part of town and is not close to the main campus, and no designated student housing
For more con's, check out the "Be wary of BU" thread. I don't know how true every thing in there is, but it does raise some valid concerns that might be worth looking into for people that are still deciding whether or not to attend.