Lulu's noodles is in an extremely convenient location for students coming from CMU, so it should be no surprise that most weekdays around lunch time the place is packed.
The few times I have been there I have found the food to be okay, nothing to write home about. The Pho was utterly terrible, and the various noodle dishes only passable. The biggest problem, though, has been with the service. You place your order at the counter, and they are supposed to bring it to you. Several times I've found myself forgotten and having to go back to ask where my food is.
All in all, it will do in a pinch if you're a CMU student, otherwise steer clear.