I've lived around here for 31 years, and, despite being only a 25 minute car ride from BWI, actually fly quite a bit out of DCA and IAD.

BWI--Although I am primarily a DL flyer and secondarily a NW flyer (both of which are at the end of Pier C), I also have used WN (Piers A and B) and UA, US and CO (Pier D). Pier C is the only security entrance that has a priority line for elites (holding DL or AA PM, GM or EXP or PLAT status, or a first class ticket). This can be useful during the 5 a.m. hour, when DL has a couple of full flights to ATL and CVG, NW has a full flight to DTW and AA has full flights to DFW and, I think, MIA. Unhappily, the TSA usually only has one or two screening lanes open (despite having 7 screening lanes set up) until after 6 a.m. As for Pier D, I have never understood why UA and CO haven't arranged for a special line for their elites.

My only amenities gripe with BWI is that DL closed their lounge (it was not a CRC, just a lounge with a full refrigerator and liquor closet, and some carrels, telephones, chairs and a TV) prior to the mid-90s, and have not reopened a CRC or worked with their partner airlines to have a shared lounge. BWI has loads more traffic than certain airports (MCI comes to mind) that have CRCs.

As far as shopping and eating, the new combined Piers A and B have quite a few options, including branches of both Phillips' and Obrycki's, two of Baltimore's most famous crab houses. Pier C, which has fewer gates than either A, B or D, has been undergoing some renovations--there are new Wendy's and Potbelly outlets down by the DL and NW gates, and a branch of Annapolis' Rams Head Tavern is being constructed next to gate C10. There are at least two other construction zones on the concourse; there is a Budweiser Brewhouse, a newsstand and a store selling Maryland souvenirs on this Pier also.

Pier D has the most shopping, and also has a Roy Rogers' (can anyone here say "Double R Bar Burger")--both the UAL and US clubs are beyond security out there.

Pier E is the international terminal--once past security, there isn't much other than waiting areas.
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DCA is a fantastic airport if you are not going by car--the metro station was integrated into the design of the new north terminal, and sits between the building itself and the multi-level parking garage. As a DL flyer, their set up works well for me--they have a check-in set up at the end of the ramp connecting the south end of the metro station with the terminal, not terribly far from the security entrance to the DL/CO/AS/AC gates (B Concourse). There are separate security entrances at all concourses--you can't go from one to another without passing out of security.

The lines at the entrance to the B concourse always seem to be long, and, although DL has set up an elite line, it is usually just as long as the regular line. On Friday morning when I went through there, two TSA grunts were having a chat rather than watching the monitor at the conveyor belt. They usually have a barker screaming in your ears, despite the fact that they have flat screen video monitors giving out the rules for the screening process.

There are both a DL CRC and a CO President's Club beyond this checkpoint--the DL room is reached by an elevator immediately after the screening area. Thank goodness that the CRC is very nice, as there are relatively few food choices in this concourse.

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IAD--They've actually improved the process of clearing security by opening up more screening lanes, and having an elite line serving all airlines, which never seems to have much of a line--I usually clear security in less than 10 minutes after joining the line. Once beyond security, one can go into all public areas airside (different from BWI and DCA). There seem to be more food choices and shopping at IAD airside than at BWI and DCA's airsides combined. DL CRC members have privileges at the NW World Club across from gate B22 (DLs gates are B-42, B-44 and B-46); PMs on AF metal can get into the joint AF/ANA club near B-47.