I think I could eat the Pad Kee Mao for the rest of my life. And I don't know quite how they make their peanut sauce, but it is heavenly. Plus, the place is an insane deal. I can get out of there for $6, including tip, and I have a drink (which will be refilled constantly if I stick around and want more), an amazing salad roll with aforementioned peanut sauce, and a vast mess of delicious noodles (and I usually end up with leftovers, unless I am starving and want to be so full I can't move).
They use no fish sauce, ever (hooray), and are pretty awesome about vegan stuff (tons of their stuff is vegan just by choosing tofu; a few dishes have egg). You can get the Thai iced tea with soymilk (from Ota!).
If you see yourself coming here more than once or twice, it is worth it to tip and be your sweet smiling self. They will remember you, and you will get treated extra-well (and you might end up with random gifts of food or beverage from time to time). But even if you're just stopping by, you will always get good food, and hot tea while you wait if it's cold out.