I'm giving Bahn Thai 5 stars because I have tried almost everything on their lunch menu and it's all fantastic. I've gone for lunch 20+ times in the past year and always leave happy.
My personal favorites:
Pad Thai- 'Ole trusty. If you are new to thai food, this is a good place to start.
Pad Si Ei- The best thick flat rice noodles in Madison! They have a great chewy texture and are not doughy at all (unlike the noodles at Ha Long Bay). It's only on the dinner menu, but will make it at lunch time if you ask. The rich flavor is incredible. My favorite thing on the menu!
Pra Ram Long Song- If you like peanut sauce and veggies, you will love this.
Wonton Soup- The pork wontons are very flavorful in a great broth. Make it a meal by adding noodles.
Service can be slow, but the staff is very friendly and they keep your beverage full!