I was pleasantly surprised with the quality, quantity, and spice level at LLX. The menu was diverse and authentic, the service friendly and efficient, and the food tastes really good.
I would definitely recommend a weekday lunch visit if possible, as the menu is very affordable ($8 for an entree and egg roll/cucumber salad) and the crowds much thinner than weekends or evenings. Further, the service is much quicker since it's not a madhouse.
The spice levels are pretty accurate-- the native Lao will make your nose a little runny, but it's not so hot as to make the meal unenjoyable. I think the spiciness adds a lot to the flavor of the meal.
I like the sweet/spicy curries best: Mango, Pineapple, etc. because you get several flavors in one dish.