My brother lives in the area (he stayed after he attained his MS from Georgetown) and he's a nerdy introverted type with a government contractor job, so you'd think he'd be a good fit, but he HATES a lot of the people there. Very Type-A environment where every overachiever from High School you can think of flocks to the area. It's nicknamed "Hollywood for ugly people," and the description is quite apt. It's all about who you know, what you do, and what you can do for them. That's not unusual in most major cities, but they're a lot more blatant about it (at the end of the day, a lot of people in DC are socially awkward nerds) and more "live to work" than even the most workaholic New Yorker. Not an easy area to make friends as the area is quite transient. Lots of people stay for a few years until they either burn out or get to move to NYC/Boston/wherever the hell they came from like they wanted to in the first place.
Some poster either on here or on another site said "Think of Reese Witherspoon's character in "Election" and multiply it by 200,000 and you have a general idea of what people can be like in DC." From my experience, the non-profit crowd is a lot more easy-going than the attorney/lobbyist/politics crowd.
Whenever I visit, I notice the segregation in some areas quite a bit, and I live in Atlanta for fucks sake! I do notice that blacks in the area are either very, very hood, or very, very educated/well-to-do types, and those two crowds do not mix, so there is a lot of intra-racial tension. Believe it or not, some of the suburbs seemed more integrated to me (outside of Prince Georges County, Maryland, which is mostly black) than DC itself.
Lots of outdoor activities, you're close to the Chesapeake Bay (Annapolis is LOVELY and lots of cute guys at the naval academy), and the Mountains are to the west. The district itself can be quite beautiful in the spring and fall, and while it gets hot and humid in the summer, it's not as swampy as Florida or Houston or New Orleans, nor does the heat last as long as it does down south. Lots of cultural events, but NYC or San Francisco this ain't, so don't expect some huge hipster scene there. It's not as meat-and-potatoes as Chicago, but it's not as cosmopolitan as NYC. 4-hour megabus ride or 3-hr train ride from DC.
And yes, it's very expensive. A 1-BR in a decent area will cost you at least $1200 a month in more popular areas of town. I know people there well into their 30's who are sharing houses in order to split the rent. Salaries are high there to cover the cost of living, but housing takes out a huge chunk of expenses. There are people who commute from as far as West Virginia in order to find cheaper housing. I-95 in Northern Virginia and I-270 in the Maryland Suburbs are both huge clusterfucks during rush hour, and the Beltway can be nightmarish in and of itself. So the closer you are to your job, the better off you will be.
I don't know much about the gay scene there because I'm usually there for family reasons, but Nellie's on U Street (which has a lot of bars and clubs and good restaurants) seemed decent, but most of the gay scene is over in Dupont Circle. There is Ziegfield's over by the baseball stadium if you're into naked men stripping. Adams-Morgan is another cool neighborhood worth checking, as well as Logan Circle and Columbia Heights. The H Street Northeast corridor is re-gentrifying, but still use caution in that particular area.
In addition to Bethesda, Silver Spring is another good close-in Maryland suburb. If you prefer the Virginia side, there's Old Town Alexandria, and the string of dense neighborhoods along Lee Highway in Arlington that run along the Orange Line Metro (which is a viable option if your job is in Tysons Corner or Reston). It's a bit more whitebread than the District or many parts of Maryland, but lots of people prefer that, so I put it out there.
The "famous" Ben's Chili Bowl is overrated and made my colon do the cha-cha slide and cupid shuffle, so avoid it like the plague.