I use a Toshiba laptop with a 18" screen. It works great and has for the past couple of years. Had another Toshiba before this one and gave it to my son when I decided to trade up. It's now about 6 years old and still going strong. Of course the new one is too big to carry around, but I no longer travel so that's not a problem and I love the big screen.
There are a few reasons you may want to consider Costco as a supplier. First, they will let you return the computer if you don't like it, no questions asked. (You can't do that at Best Buy or most any other store.) Second, as GB said, they extend the warranty at no extra charge. They have what they call their "Consergie" service that you can call anytime for help in setting up, etc., again at no cost, and finally, the stores I visit here do have reasonably knowledgeable people to help you with selection. Not every one of them, but ask for someone who knows his stuff. They're not on commission, so they give honest opinions.
Many of the new laptops offer 4 to 6 gb of ram, and the more the better, and most have large hard drives. The speed of the processor is probably more than sufficient on all of them for what you need. It's the games and very heavy graphics programs that need really high speed. Make sure the keyboard is comfortable for you. Some have small keys squashed together. My wife had a 12" unit that I absolutely hated because the keys were so close together that I was always making typos.
