Weather wise Boston is pretty tough but because I know so many more people there I'm actually thinking of moving back.
As far as American cities go the two ones I think everyone should see is San Francisco and New York. Both great cities with a lot to do. SF is about two hour drive from me and NY was a 3 oe 4 hour bus ride from Boston. Boston's ok but cannot compare with NY. Wish I had taken some trips to CBGB in the early days.