I used to be a laptop salesman/technician.
My personal opinion:
Stay away from dells/alienwares they're nothing but trouble.
Do not buy extended warranties unless you're hard on laptops and you plan on getting the accidental damage coverage.
My personal favorite brands are HP and Toshiba.
As the tech for over a year I only worked on 3-4 toshiba's and they were ancient. I had tons of dells that cost more to fix than what they were worth. I also worked on alot of hp's but it was 99% stupid stuff like "hey i looked at this 'website' and now I have this virus" and that is not the manufacturers fault at all.
Right now I'm rolling the HP ProBook 4525s which is my favorite laptop i've ever owned so far. Dual core, 8 gigs of ram for under 500 bucks. The outer lid is aircraft grade aluminum, as well as the inner palm rest. The keyboard has a built in liquid drain so if something is spilled on it your computer should be good to go. The touch pad is multitouch so you can pinch and zoom like an iphone/droid. Pretty cool machine for my uses.