Big screens might not be a good way to go for crowded auditoriums and somewhat limited study spaces you might be using your laptop.
I'm specifically considering the W5 model, which is a long-battery-life (8-hr), fanless 12.1" ultraportable. The goal is to have a computer that I can confidently stick into a backpack with my books, without a charger, and take on the bumpy public transit and around school for three years with almost no chance of breaking. The main concern is (of course) price. At $2000 I can get the bare bones specs. For around $3000 I can get the specs bumped up to something good, maybe too good.My school's deal with Dell means I would pay around $1200 or a little more for a Dell Latitude D620. The W5 is so much more expensive compared to this, but with the Dell I am sure it will break sometime during three years even if I baby it, let alone give it the kind of casual treatment I would like. Even with a complete Dell warranty, not having my computer even for a week could be a major disruption.
Guess it's a matter of taste, I find 17" to be a tad bit too big for auditorium desks, I'd go for a 15". Even the 12.1" are pretty decent for classroom use actually, but you'd probably want to invest in an external monitor for homework then.