Campus life: it's about as active a campus as I've ever seen. Vibrant academic community. So many things on-campus such as the Yale symphony, theater (plays), art galleries, science museum, and sports (although the quality is Ivy, so you know what to expect). Lots of interesting academic talks or cultural festivals going on. It's a wonderful academic community.
The city: I hate answering this question because some people really like New Haven. I personally hate it. The problem is, there's a big poor population that is disenfranchised from the campus, and there's a bit of animosity from the city and the university. Petty crime is an issue. However, there are some good restaurants here and a surprising number of bars. The biggest problem is, if you're coming from a big city like a New York, Boston, Chicago, or DC, it's a bit of a change.
Professors: I think they're wonderful. Of course, my experience as a PhD student is quite a bit different than what a MPH student gets because my focus is on research. But I can definitely tell you that what the profs work on is genuinely interesting stuff. I must say, though, that since Yale is very small, there are several niches that the profs work in, and if you don't see faculty working in a specific area you're interested in, you'll be out of luck to get training in that area.
BU vs. Yale: The schools are DRASTICALLY different. BU is clearly more focused on an integrated community and research methodology, whereas Yale is way more focused on research methodology. At BU, unless you are a Epi/EH/BS concentrator, the methods, computational, and statistical courses are optional. No matter your discipline at Yale, you'll be taking at least a few courses in those research methods. BU also has a much wider range of classes (because the school is also much bigger).
For someone like me, Yale is a much better fit academically because of my research interests (no faculty members did research in what I was interested in), so I'm very happy at Yale.
