I noticed the DDs everywhere in Boston as well. They are the Starbuck's of that city it seems (this coming from someone who lives where there is a Starbuck's across the street from a Starbuck's). The coffee isn't bad at DD but not my favorite.
I personally prefer to brew my own (coffee press).
If I do get coffee at a coffee shop I tend to go to the hole in the wall type places for a few reasons (free wifi, better tasting coffee, and personal service). Also, the food options are usually better at the mom and pop shops.
Has anyone tried the recently updated McD's coffee? Pretty good stuff IMO.