computer engineering is a very small department and they are probably excited about the prospect of having you on board. if you are on the fence about columbia i would suggest you come up with some good questions that will help you decide before you make the phone call. if you are already certain you will be going to columbia then use the phone call as an opportunity to make a contact with an influential prof in your potential department and use it as the first step to securing a research opportunity (or whatever computer engineering people do that is equivalent to research) or getting an idea of what the department is like. It is never too early to start off on the right foot with the faculty.
as you can read through my posts - i am an unequivocal columbia lover
i think that goes for all the current students and alums on this board (yes, even C02 loves columbia, he's just [relatively] old and cranky) ...i think the fact that there are so many active students and alums on this forum shows that columbia leaves a great impression on you that you want to get the word out about it. also it shows you will find alot of awesome down to earth people at columbia.