What do you want in an OS, and how does Windows fail to serve this want?
Try running Knoppix to see how Linux handles your hardware.
RedHat Linux has been replaced with the Fedora project. Try
Fedora Core 1 if you want to see what RedHat Linux was all about. I've used it, and it's pretty nice. The Core 2 testing version is out, so give it a try first.
Other distributions to consider: Xandros, Lindows, and Mandrake.
However, keep in mind that Linux isn't intended to be a Windows replacement, but a different operating system altogether. In fact, each distribution is a different OS, some radically different from others. You might consider trying a lot of different distributions, such as Xandros and Lindows or Debian and Slackware, to find what suits you best.
Even then, because Linux uses X11 for its GUI, there is no de facto user interface. X11 only provides a system for creating programs that manage window (Window managers), programs that have windows (Applications and everything else), and a very primitive library of drawing routines and event handling functions.
Built on top of this are many different "widget toolkits" providing sets of controls for things like buttons, menus, etc. which are called widgets on X11. The biggest two are QT and GTK+, which the two major Linux desktop environments use (KDE and GNOME respectively). Each widget toolkit usually has a radically different look and feel, so you may be using a variety of applications that look and act differently, although KDE and GNOME have enough applications where you might never use any others.
Window Managers are programs that manage Windows. That is, they draw title bars, window borders, etc. and handle the moving, closing, killing, minimizing, maximizing, focusing, etc. of windows.
A Desktop Environment provides a unified Window Manager, Panel, widget toolkit, and file browser. They usually have lots of applications that use their widget toolkit, and in the case of KDE and GNOME, development framework. However, you can still use any X11 application regardless of window manager or desktop environment.
The end result is that you can usually customize the user interface to look and more importantly act/feel exactly how you want it. However, the other problem is that you may have to try a lot of different window managers or desktop environments and configurations to find what suits you best.
What I'm currently using (Gentoo Linux) is definitely the best desktop Linux for users who need performance. It gives the flexibility and power I need, doesn't separate runtime and development code, is easy to update, and most importantly outperforms every other distribution (as well as Windows) by a factor of 5-10 when it comes to application load time and speed. However, it requires a lot of knowledge and time to install correctly, so mostly experts and intermediate Linux users install it.
