Alright so some advice from a fellow CS student
Any laptop will do you fine for CS studies. Though for the sake of your backpack keep the laptop choice reasonable. For instance, the laptop Boz referred to, if it's this thing: http://www.newegg.co...N82E16834231090 - I've seen one or two used by fellow CS students. That thing is great if you're interested in a desktop replacement that you can take to in study rooms or lounges for long term coding sessions, but any other use and that weight will kill you. That's an 8.5 lb laptop. I was lugging around a 5.7 lb ThinkPad W530 laptop for work and that was already heavy enough. Great laptop though (see below...)
If you're looking for ASUS laptops their midrange VivoBooks and Zenbooks do just fine. Well priced machines that look pretty decently built.
If you want something that lasts, then have a serious look at a ThinkPad. They're pricey, they're ugly, but they will sure as hell last you for four years and they can definitely take a beating. The W530 I used was a great machine, powerful as a pseudo-desktop replacement at 5.7 lb, but again it's a desktop replacement machine. You'll want something you can comfortably put in your lap or lug around to classes to take notes, which you should be doing anyway . I quickly searched and a ThinkPad T431S is going for $786.75 with an employee code. It's an Ultrabook but not as thin as the Carbons, but the Carbons start at $1000+. Alternatively you can aim for the T430s if you're looking for a dedicated graphics card for occasional gaming. Don't aim for the IdeaPads - I'd rather pick up an ASUS laptop if you're aiming in that price range.
Now Macs. You might not like them, and they're already out of your specified price range, but there's a *lot* of people who use Macs on campus, and in computer science. For what it's worth, they're also great machines that are better built than most consumer laptops (maybe except ThinkPads, heh). Most people I see using Macs can get away with using just the touchpad while a lot of Windows guys are lugging mice around. Obviously don't buy one if your workflow is Windows or Linux-centric and you don't plan to learn OS X. Anyways you can't go wrong with a Mac - even an Air should be sufficient. Just be sure to pick up a new Mac - Apple tends to drop support about four or five years into the life of a new machine.
I personally have a Dell laptop - Alienware m11x R2 - and it's a pretty decent laptop that barely passes as a gaming laptop, while being small enough to lug to classes for notes. It's still running well almost three years into its life, besides the well-known hinge issue but that was fixed. Their warranty's alright, but their support for drivers is quite lacking. Otherwise these days I'm seeing increasingly fewer Dells around campus - most people have Macs, ASUS laptops, or ThinkPads. My first laptop was an XPS m1210 and that was a piece of crap.
Some friends have VAIOs and swear by them. Also great machines, if a bit pricey.
HPs - avoid. Their laptops from the late last decade sucked horribly. Acer - probably avoid as well.
I've only seen one professor and one student bring a Surface Pro to campus.
Do you need a touch-capable machine? I would say not - you'll be spending most of your time in IDEs or even in Linux.
Hope this helps The overall point I would drive across is, don't think too much about how much you paid for the laptop when you first got it. If that means in four years you can still have the same laptop without it having broken hinges or all run down, then it's worth it.