Lived there from Sep 2001 to Sep 2004.
The public transport is of high quality, but the areas of coverage are not the greatest, and there's a major drawback which is that it stops running at night. That's crazy. Maybe they changed it since I left.
Living in the district has two distinct qualities to it... first, you're closer to the cool stuff which is mostly all right around 14th and U st NW, and Dupont Circle and Adams Morgan which are just west and just northwest of there, respectively. As a part of this being close to cool stuff, you get the 202 area code for your cell phone, which is super dope and makes you immediately be all cool and stuff. BUT. The downside is HUGE. State income tax in DC (which is not actually a state, go figure) is *NINE PERCENT*. And it's a stupid-expensive town. So when I moved there from Chicago, not only did all my expenses go up, but 6% of my gross pay also disappeared to pay for DC to not be a state. TOO expensive.
Something funny about DC is that there's this weird feud between Maryland and Virginia people. It's not real, I don't think, and nobody *really* cares about it, but people love to talk shit on each other for living in the one state or the other.
After 2 years in the District (Columbia Heights, which I liked just fine as a neighborhood until being robbed on my block at what may or may not have actually been gunpoint), I moved to Arlington and liked it a million times better in every respect except that I was farther away from the 14th and U area and thus had to make more of an effort to get there than I did when it was a 10 minute walk.
It's really quite pretty, the whole area, with lots of trees and hills and rivers and Chesapeake Bay etc if you get out far enough. Even inside the district, there's lots of trees, much more nature-feeling than Chicago is. Can't speak for Pittsburgh.
There are places to go in Arlington as well, on Wilson Blvd and Arlington Blvd. The area between the Clarendon and Courthouse metro stops is where a lot of Arlington's bars are concentrated.
I lived just west of there, in Ballston. Had a great little Cape Cod style house with a basement for rocking out and a big backyard with a small jungle in it, for $1400 a month, which really wan't bad at all. I had one roommate there, we each had our own floor of the house, and we spent a lot of time in the basement playing Vice City and drinking berrs and playing rock music. That beat the hell out of my one-bedroom apartment in a get-robbed neighborhood in the district for $900 a month.
Something about DC is that it is a supremely American town, maybe one of the most "American" towns there is, in the sense that there are people from all over the world that live there. Many of them are in politics or whatever and are fancy-pants folks, but there are also refugees from El Salvador and Ethiopia and other places, too.
Mostly I found DC to be very stratified; the poor people are poor, the rich people are insanely rich, and there are a good handful of folks inbetween, but not so much like you probably have up your way. It wasn't a big manufacturing town like lots of the midwest cities are, so it doesn't have the same kinda entrenched blue collar crowd. I knew a guy who moved out of DC because he was so sick and tired of people asking "so what do you do?" (which is the default question in DC) and when he told them "I work at Enterprise Rent-a-car" they had no interest in any further conversation. I never felt that, because I've yet to meet a person who wasn't interested or at least confused when I describe my job which is a job that nobody even knows exists for the most part. So, if your job there is gonna be a cool one, you'll do well in those conversations. Ugh.
It gets hot as fuck in the summer, and humid too. The winter will seem like a fucking joke to you. Everybody goes cuckoo if it snows 1". The winter there is a cakewalk compared to Pittsburgh, I'm sure. Lotsa people out there told me "I love Chicago but I would never move there because it's just too cold".
What else...
Expect your car window to broken and little shit to be stolen from your car every couple years unless you're dilligent about never leaving anything in it. And maybe even if you are, depending on what neighborhoods you spend all your time in.
Always steer the fuck clear of the people with the red-white-blue license plates that look kinda like an old Ohio plate, cause those are Diplomat plates. They have their own laws. One of those laws is, they always win and you always lose.
Be ready to be pummelled with politics from almost every direction on a daily basis. It's kinda the whole point of that town.
Also, be ready for Masonic iconography on a level you've probably never seen anywhere else. Those fuckers are all up in that town, bigtime.
If you wanna be funny and seem like you're not as much of an out-of-towner, when talking with friends, refer to the Washington Monument as "the Big Dick".
That whole Mall area, everything from the Capitol over to the Big Dick and up to the White House, all of K street, up 14th street, embassy row, Rock Creek Park, these are all really interesting and cool things to look at and hang around. I lasted almost 3 years in that town before I was ready to come back to Chicago and love it like I never loved it before.
Northern Virginia was good to me. I like Arlington. I like Falls Church. I like Ballston. There are other areas around there, too.
Oh yeah, almost forgot, the vehicle inspections in Virginia are pretty harsh, as they are in DC as well. And in Virginia, you have to pay a vehicle tax every year that's based on their assessed value of your car. Extra bills! Yay!
If you live in the district, in addition to the 202 cell phone, you can get the "Taxation Without Representation" license plates, which kinda fucking rule. I was sad to lose those when I moved to Arlingon. Oh, and when you go back to Pittsburgh to visit family or friends or whatever, when you go out to bars and they card you, and they see a Washington DC license, you can act like you're *pretending* to be a normal guy, but really you're CIA or something. That was always mildly amusing for me.