I just went to Sen for a work celebration lunch and it was rewarding in every way. The atmosphere is fun with warm colors, ethnic accents, and a mural of elephants on the walls. The service very polite and prompt. We didn't have to wait long for our food--of course, we got there early. It gets crowded later in the lunch hour.
I ordered yellow curry with shrimp and it was to die for. The curry was flavorful with just the right amount of spiciness. The shrimp were cooked perfectly, and the jasmine rice was good too. I am no expert on Thai food, but this is excellent by any standards of cooking.
If you're in the downtown area and like Asian food I recommend Sen very highly.