Is indeed getting pretty depressing, but I guess there's finally some renovations underway. I'm usually through there a few times per year visiting family (back since most of my BOS-BWI travel was on AirTran starting about 2003), and security at D has always been frustrating. Some of the worst lines I regularly encounter, especially when departing on early morning flights. During one round of construction, it felt like the security line was stretching all the way behind the ticket counters down to terminal E.

I see the current terminal map from the airport shows D1-5 as all closed. In the last couple years it's seemed like B6 has been jumping around the lower D gates a lot, I guess that's likely to only get worse as the badly need rehab continues. There's a ton of gates in D, but unfortunately way too many of them are in the old US commuter gates out at the end, which last time I was there were all but completely closed up.