When it comes to Linux, there is no one size fits all answer. But, unlike other desktop operating systems, Linux doesn't try to squeeze you into a system's that's too large or too small. Instead, Linux offers a wide variety of distributions and one of them is likely be the right one for you.
Linux, you see, is a family of operating systems. They share the same father, but each distribution has its own personality and its own audience. For example, if you really wanted to, you can have a Linux distribution that looks and act like Windows XP, but which underneath its Microsoft-like surface is actually running Ubuntu Linux. Or, if that doesn't strike your fancy, you can always make the popular Ubuntu distribution into a Mac OS X look-alike.
How to give Linux a try
Better still, you can find a Linux that will do what you want it to do. After all, despite silly tales of how you have to be some kind of technical wizard who chants "awk, grep, sed" at a shell command prompt to use Linux, anyone can run Linux these days. The default Linux desktop KDE or GNOME graphical interfaces may not look quite like the ones you're used to but they're every bit as easy to use and as powerful. Yes, once in a blue moon you may need to modify a configuration file by hand, but you'll need to do it no more often than a Windows user has to do the exact same kind of thing with the regedit command.
The real question isn't, "Can I run Linux?" It's "which Linux is best for me?" Here's my guide to help you find the right one for you.
I just want to play with it and see what Linux is like
No problem. There's a variety of ways to tinker with Linux and never have to buy or install anything permanently. For that matter, you may already have Linux on your present PC and never have realized it. Many laptops come with an instant-on setting that lets you browse the Web and check e-mail without ever booting up. If your notebook does that, chances are you're already running an instant-on Linux like DeviceVM's SplashTop.
If not, there are many other ways to give Linux a try without any trouble.
I just want it to run
OK, what you need to do then is to buy a netbook, laptop, or PC that already has Linux installed on it. Once upon a time that was hard to do. These days it's no trouble at all to find vendors that offer Linux already installed and ready to go.
The best known major vendor that wants to sell you a computer with desktop Linux ready to go is Dell. Dell usually offers three to four systems with Ubuntu already installed. The mix always includes at least one netbook and one laptop. At the moment, my favorites of their selection is the Mini 10v, a nice little netbook, and the Studio XPS 13, a powerhouse laptop.
These are easy-to-use, handy systems for both individuals and SOHO (Small Office/Home Office) users. But, say you're an engineer and you want a heavy-duty system with a business class operating system, what then? Dell has you covered again with its Dell Precision Workstations with Red Hat's RHEL (Red Hat Enterprise Linux) WS 5.3.
You don't have to go with Dell though. Other major hardware vendors like HP and Lenovo also offer pre-installed Linux on desktop systems. I'm loath to recommend them though because, frankly, they make it very hard to find their Linux-powered systems. Your better choice is to go with a smaller company that stands behind its Linux PCs like Los Alamos Computers, system76 or ZaReason. For a more comprehensive list of companies that sell computers with Linux ready to go see LXer's Pre-Installed Linux Database.
I want an easy to use Linux
Ubuntu is the default answer for anyone looking just for an easy-to-use desktop Linux with a huge, friendly user community who are ready to help. It has that reputation for a reason: Ubuntu really is easy.
What Ubuntu doesn't come with, by design, is some popular proprietary programs such as Adobe Flash or Reader. If you want those programs, but you don't want to bother tracking them down and installing them with the Ubuntu Software Center, what you want is a Linux distribution that comes with these programs either already installed or makes it really easy to install them.