Agreed. I was confused when I noticed this thing yesterday and tried to google it, and found a couple different plans... I don't know what the base looks like, but hopefully they are preserving the facades of the older buildings (I think they are...)
The massive nature is the biggest outlier here, but the Hill is so cramped I don't think there will be any chance to really appreciate how hulking it is, since you won't ever be able to see the full building from any vantage. It's the disruption of the neat fabric of old rooftops that I dislike the most... although to be honest, I don't think this is that bad and if it doesn't disrupt the rooftops when seen from their best vantage—from the Longfellow Bridge—I'm fine with this.