I'm a university student looking for a new laptop. I'm a computer science student, if that makes any difference.

Must be 13 - 14", and around 2kg, preferably lower.

Primary uses will be taking notes, programming and possibly some gaming. I definitely don't expect to have maxed out settings, although low on native resolution would be nice. I'll mainly be playing Call of Duty, L4D2 and Minecraft.

I have a few choices in mind, but due to lack of reviews, I'm not sure what to get.

Asus U31SD - i5-2410M 2.3GHz, Nvidia 520M, ~$1500
Concerns - Build quality - apparently its predecessor had flex.

Lenovo Thinkpad Edge E420 - i5-2540M 2.6Ghz, Ati 6630M, ~$1500
Concerns - Battery life, might be too heavy to lug around all day?

Sony Vaio S - i5-2410M 2.3 GHz, Ati 6470M, ~$2100
Concerns -  This one's a bit over my budget, but if it's good, I don't mind considering it.

Help will be greatly appreciated. :)