Buffalo & Bergen - sells bagels and knishes. I rarely eat bread so I tried a collard knish. All I can say is that collard greens don't make a knish taste better.
DC Mediterranean - mediocre middle eastern food. I had their falafel, kibbee and various pies.
Rappahannock Oysters - excellent oysters at a decent price. Also tried their lamb and clams - decent for the price.
RIS - expensive small bowl of rather bland curry goat stew.
DC Empanadas - fancy empanadas flavors that I don't like.
Spices and Tea shop - both way overpriced.
After several trips to Union Market, my conclusion is that it ain't worth the time and effort for me to get there.
The best things in the neighborhood aren't even in Union Market: New Youngs Deli and Litteri's. Chinitos Burritos isn't bad either, but it's closer to Gallaudet. Union Market is where you go to drink coffee and look at other people drinking coffee while looking at people drinking coffee.
The crab cake at Rappahannock is the best I've had out in DC. I have never been disappointed in anything from Red Apron, from beer to sandwiches. A cheese and wine flight at Righteous Cheese is a great way to stay a little longer.
There's great stuff at Union Market. I'm a very happy repeat visitor.
Just to clarify, I live in VA and it takes around 30 minutes for me to get to Union Market without traffic. My opinion is written from that perspective. If I lived closer, I would pop into Rappahannock. But I wouldn't drive 30 minutes to Union Market for the current roster of vendors.
I like the smoked fish from Neopol Savory Smokery and the bread from Lyon Bakery. You can buy the fresh herbs at the produce stand by any amount you need, which can be handy and save money. Trickling Springs Creamery has some very good products. Union Market also has pop-ups from time to time that add to what's available.
I would go back to Union Market.
The porkstrami sandwich at Red Apron is pretty good, and the meatball sub is terrific. Oddly enough, what really makes the sandwiches stand out isn't the meat as much as it is the bread. That said, a lot of people may complain about the price in relation to the size of the sandwich, which is a somewhat legit complaint as the sandwiches are not that big. However, they do fill me up and I enjoy eating them, furthermore, unlike a lot of folks, I don't feel the need to consume a foot long sub of 2000 calories for lunch and don't really get angry if I receive a sandwich that is anything less than that. They also have a small but very well curated beer selection. I also agree with you about Rappahannock Oysters - very good oysters at a reasonable price for DC. Otherwise, everything else there seems not that special but very, very pricey.
I went back to Union Market because I heard Toki was still doing a pop up there. Unfortunately, the guy there was burned out on cooking ramen, so on Saturday he served a Thai pork meatballs cellophane noodle soup for $12. I liked the flavor of the soup but it was very salty. You can get a similar dish at Bangkok Golden III, which is why I thought it was unfortunate.
At 11, I sat down at the Rappahannock counter. They were serving sea urchin with dashi, dashi crumble, and foam out of the shell for $20. There were only 2 lobes, but they were fairly large in size (nevertheless, they would only cost about $10 at an expensive sushi bar). I had a half dozen grilled oysters for $12.
Finally I went to Bidwell and had their lobster tacos ($10 for 4 bites). Wrapped into a roll were some tiny bits of lobster with lots of blanched spinach. I didn't like it at all, especially since the lobster was a little fishy.
I bought some fantastic sea bass last weekend from the Fishwife. Yes, it's a little expensive, but the quality is leaps and bounds better than what you get pretty much anywhere in the city. They are definitely on par w/ Blacksalt market.
I have really enjoyed the Toki pop-up. And TaKorean. But I also like DC Empanadas. I guess I don't think it's that hard to get to and I enjoy seeing what's there and shopping around.
For me, it's only 15-20 minutes and I find it a worthwhile excursion.
Love some of the small producer items available in one of the dry goods merchants (can't remember the name) -- the Big Spoon nut butters and Baba's pickles.
Got some nice meat from the butcher, they were happy to break down into a smaller serving I was looking for.
Trickling Springs has nice dairy (although you can order some of it through Relay Foods as well).
Enjoyed the pies I've picked up from RIS.
Lyon Bakery bread is quite good.
Vegan foods and juice nice, in line with other places in town.
The produce stand was my only complaint (squishy potatoes) ...but I wasn't really expecting much from that.