O Ya is famous for being named Frank Bruni's #1 most intriguing new restaurant outside of New York: http://www.nytimes.com/2008/03/19/dining/19count.html?pagewanted=2&_r=1&ref=dining
It is also very expensive, especially by Boston standards (I spent about $230 on just food costs, although I ate about 1.5 people's worth) and I doubt you can really get out of there for less than $130.
The menu is extensive, focusing mostly on their versions of sushi (two pieces per order) and sashimi (three pieces per order), but also features cooked foods like kurobuta pork, wagyu beef, poulet rouge chicken, and other goodies. The tasting menu consists of one piece each of 15 different items on the menu, but I chose to order a la carte. I will list everything in as close an order as I can remember to being served the dishes.
Shima Aji and Uni with ceviche vinaigrette and cilantro (sashimi)
The ceviche style clearly comes through with a heavy citrus flavor and a little kick. Nice start to the meal and a good mix of textures and flavors, although the uni was noticeable but not as strong as bursting with freshness as I would have liked.
Hamachi belly with yuzu soy marinated sea urchin (sushi)
I love hamachi belly but neither ingredient seemed to stand out like I'm used to. I was hoping for the strong uni and hamachi flavors to clash and create fireworks but it was disappointingly bland for what it was.
Wild bluefin toro 2 ways: spicy mentaiko mayo and republic of georgia herb sauce (sushi)
My waiter recommended the one with the herb sauce but I ended up asking him for one piece of each combined into one order. He was right. The mayo didn't really do anything for the fish but the earthy herb sauce had such great presence on top of the fatty fish.
Fried Kumamoto Oyster with yuzu kosho aioli, squid ink bubbles (sushi)
A tasty mixture of flavors and textures, with a nice touch provided by the squid ink. However, this was my first inkling that their sushi rice is not top notch.
Kin Medai with white soy ginger, myoga, lemon oil (sashimi)
The lemon oil is too strong and comes out first.
Chilled Homemade Soba Noodles with Santa Barbara sea urchin, nori, fresh wasabi, and scallions
This was nice and tasty but nothing special and certainly not something I needed to taste here at these prices for such a small portion. The noodles seemed a little thinner than normal soba noodles, but did have flavor and bite.
Yuzu Brined Ballotine of Chicken Wing with napa cabbage and shiitake stuffing, and homemade kimchee
This sounded wonderful but they must have put too much of the toasted sesame seeds since that was mostly what I tasted. I couldn't decipher all the other flavors that went into it and this turned into an unfortunately expensive piece of sesame chicken.
Silken Tofu Tempura with wild hedgehog mushrooms and shoyu broth
This dish was unfortunate for my wallet. It was in the truffle and eggs portion of the menu despite not having any truffles or eggs. It used to have truffles but they removed it from the dish but didn't reduce the price. An unfortunately expensive piece of agedashi tofu (not really, as you can taste the tempura batter, but you get the idea). The shoyu broth was nice although too sweet to just drink up. So I ordered a side of rice (they only had sushi rice) to go with it. A closer inspection of the sushi rice in this manner did lead me to believe that it was not top notch, and had a tendency to mush more than say the rice at Yasuda's. However, the vinegary rice with the sweet shoyu broth turned into a very interesting and tasty mix.
Hamachi with viet mignonette, thai basil, and shallots
At this point I asked the waiter what dish would the chef absolutely say that I must have before leaving. This was the chosen dish and my waiter was right yet again. Just a perfect mix of textures and flavors. It really felt like 3(flavors)x3(textures)=9 different things going on in my mouth.
Grilled Sashimi of Chanterelle and Shiitake Mushrooms with rosemary garlic oil, sesame froth, homemade soy, and sesame brittle
This was a very satisfying dish that certainly seemed to get the most out of its ingredients. I think I would have preferred it if it was served hotter. While I liked this dish, it was not my favorite as opposed to Bruni.
Foie Gras with balsamic chocolate kabayaki, raisin cocoa pulp, and a sip of aged sake (sushi)
This was wonderful and a great way to end the night. The foie melted in my mouth and the sip of sake went wonderfully with it. I thought it was interesting that this was served as sushi and not sashimi, but it worked.
The place itself is in a little nook and my cabdriver hadn't even heard of the street that it's on. The door is also not immediately noticeable from the outside. Once inside, it's mostly dark except for lighting right above the sushi bar and the light from the kitchen, as the kitchen door is pretty much kept open all night. While there weren't many diners and the place isn't big, most people came in groups and it was a chatty atmosphere. I sat at the counter which was lined with stools. I recommended to the chef/owner afterwards that he needs to change them and hopefully he will listen. When you want your customers to sit for more than an hour enjoying food, you need to offer them back support. There was a nice waft of truffle throughout the night. After it was all over, I went back outside, walked about half a block, and realized I was standing right in front of the South Station bus terminal. Right in front of where I've taken many many Greyhound and LuckyStar buses (I do not use Fung Wah) back to NYC. I had no idea the restaurant was right there. I will definitely be back with a better idea of what to order (they had a slab of bluefin otoro that looked amazing).