My biggest gripe about Dunkin's coffee is the consistency. It has potential to be quite good IMO if they had more strict rules on how they make it. I don't know if its the measurements they use, the time it takes to brew, or how long they let it sit before brewing a fresh pot, but its never the same.
I've had some really great coffee from Dunkin Donuts and some really horrible coffee from them too. Same location, different locations, you never know what you’re going to get.
If Dunkin could match the consistency of Starbuck's, I think their coffee would be terrific.