Former SMU student,
To answer your question. No SMU students are not pretentious. The school does have a high percentage of wealthy kids mainly from the Texas and the south. Since SMU is small and not very diverse it can seem a bit insular. I enjoyed my time there and had a lot of fun. Everyone I met was welcoming. However it is a small campus with a strong culture and this can be overwhelming and perhaps why some people find it to me pretentious.