I studied for a degree in IT (and also Elec Eng) and started out with a generic (non-Apple) 15" laptop which must have weighed about 7lb! I got sick of carrying it to and from home, and around campus for lectures, so I usually didn't bother with it most days. Having such a large laptop was also pretty cumbersome during lectures. I only wish I had bought the original 13" MacBook earlier!
Long story short, I'd cut away the 17". You might say you won't notice the weight now, but tell me that in six months time when you've been lugging it around for eight hours a day! IMHO, the 13" MacBook Air will be sufficient enough for anything you'll be tackling with in IT and it has a vastly improved battery life. You can always connect it to an external monitor at home if you need the extra screen size. However, if you still want something bigger/more powerful, I'd suggest a previous model 15" MBP.
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On the topic of apps/programs, a productivity suite will be vital, such as MS Office or iWorks. Depending on what stream of IT you'll head down, you may require different operating systems (Windows or possibly even a variety of *nix, ie. Linux) for software development or networking assignments. You can always dual boot with Bootcamp or use a VMWare. Although, if you're going to run virtual machines, then a Pro is probably the way to go. Also, if you've got your own Dorm, then it may also be prudent to invest in a cheap black and white Laser printer for the plethora of lecture notes and assignments you'll print!