I just talked to some people at Columbia and thought it would be good to share. TC is actually very well-regarded among Columbia schools. Some TC students are not happy with the fact that some of their classes are rather crowded ( 40-50 students/class!), but considering that some classes at SIPA and Fu School of Engineering ( where people I communicated with are attending) may reach up to 100-150, I think that's not too bad. Still, it's funny because Columbia is a private school; I expect smaller-sized classes. Other than that, as dpgu800 pointed out, TC students can freely register classes at Columbia, and many people take advantage of that. Sounds pretty good to me.