Well, if one were to take a quick look at the "classic" *nix screen, you might say it looked like DOS. Albeit, something that only vaguely had a passing resemblance to DOS and was approximately 100x more powerful and configurable.
X is the UI (user interface) that "simplifies" the use for most of us. Graphical, configurable, people use different shells (AfterStep, GNOME, KDE, et al) that enhance/change the UI to their needs. Each is configurable up the wazzoo. Heck, you could even get it to look like your Windows desktop if you wanted.
So when someone says "depends on what you want to do with it," they really mean that.
If you have the space, time and patience, you could always download a distro and try it out on your current partition. Linux4Win comes to mind, as does Mandrake (7.1, at least that I know of) will let you install a "fake" partition on your HD. It creates a very large file which it uses as a virtual-partition for linux. Then, if you like it, go all out and 'nix Windows. Pun intended.