Let me preface this by saying that I only interviewed at MGH. I canceled my interviews at BWH and BIDMC b/c I realized that I didn't want to live in Boston.
I was impressed by my interview at MGH...not for the obvious reasons, but because it was completely opposite of what I thought I was going to see. Although it is a highly academic department, I was surprised (pleasantly) by the lack of focus on resident research. One of the chief residents stated that although there are TONS of research opportunities available, research is not forced upon any of their residents. The residents actually have to seek out opportunities for research. The other pleasantly surprising bit of info was, IMHO, the lack of arrogance amongst the residents. Although members of a well-respected Anesthesiology department, the residents weren't nearly as caught up on the fact that they were training at "MGH" or "Harvard" as other residents I met at other programs.
With all of that said, there are definite down-sides to the program that I found as well. First off, the residents are their workforce (same is true at BWH?). I believe I was told that there are only 12 CRNAs for the 40-50 ORs at MGH...guess who is doing all of the work? Consequently, when asked about moonlighting opportunities, one resident said: "You still have to stay under the 80 hr. work week, so even if you wanted to, most of the time it's difficult to find the time to do it." (factor that into the $1800-2000/month rent in Beacon Hill). Finally, it's been mentioned several times on SDN, but multiple residents commented on the weakness on cardiac and regional anesthesia...apparently steps are being taken to correct both of these (decreased # of cardiac fellows/new community site). but I think it's too early to tell.
Overall, I think MGH is a strong program....if nothing else in name (depending on what you are looking for). I can't personally compare it to any of the other Boston programs, but from everything I hear from classmates of mine, BIDMC is the way to go. Okay, it doesn't have the "name" of MGH or BWH, but it's still Harvard, come on...