I had a good first experience at Cowfish when it first opened, it was packed with all seats taken and i snagged a spot at the bar. My general rule of thumb is to go to the bar if it's busy and often bartenders wont let your food suck.
Months later I returned and it was middle of the week and it had just opened. The fishtank for the cowfish was cloudy and no one seemed to want to be there. It was hot and they tried to seat us outside despite being one of the first three parties on a hot day. No thanks. Food was "meh" and service was acceptable but not at all special.
Similarly, I've been to Morimoto's three times (four times if you count the pre-opening walking tour). The first time was the walking tour where all the hopes and dreams of how it would operate were explained - things like the Forbidden Lounge have not played out as designed because they need the seating. In theory you could only be up there by asking for it by name and using the side door and special staircase with the taiko drums. Anyways - wonderful experience at the Forbidden Lounge on my first real visit dfuring the grand opening. They had imported liquors they technically shouldnt have in the US and I took advantage of that.
Second visit, real reservation, packed but seated quickly and had more normal food (at the Lounge i had mostly drinks and smaller plates followed by dessert). It was quite good. And then just a few weeks ago, midday weekday and it was still busy but got us in quickly, again on the first floor, and the food and service were both good.
Some places are just run better. Toothsome was good when i went, and my friend who had been previously suggested it so she had good experience prior and on our visit too.