I am using an older Dell Latitude Duo XT, converts from tablet to clamshell laptop. I'm running Ubuntu on it, I really like the new Unity desktop layout. And Ubuntu is not difficult to install these days, there's a "build" (meaning installable version) for almost everything reasonable on the market. Not like years ago when I first did a *nix install, and needed lots of help.
I'm twitchy about Windows, and ditched the Windows Vista this unit came with.
Go to the store, handle and look at everything on display. How is the screen size? The text size? How does the screen size handle the window for all the things you like to do? Figure out what you like, write down all the specs (including the numbers and words you don't understand) then go home and read at least five reviews for each machine. What's the most common complaint? The most common positive comment? Then look on-line, see how the prices for Amazon, Newegg, and every other large-name vendor compare. Avoid the smaller and rebuilt-only vendors - if you're not expert in handling slightly tweaky machines, you want to stick with new or a manufacturer's rebuild.
FYI, for all the problems Apple has, its remanufactured prices and quality are excellent, often when you order one the one you receive is actually upgraded from what the web page described, and they hold their resale value better than any other non-customized make on the market. On the other hand, with Apple there is their well known dislike of supporting Flash.
I'm no geek, this is all stuff I've learned on my own. Always buy the largest screen you can afford, always check reviews, always ask yourself is the negative reviewer has a clue of what they're complaining about, always ask yourself if the positive review is someone glad-handing him/herself because they wanted the hottest machine advertized and are going to like it no matter how cr4ppy it is.