Linux made easy, Ubuntu and OpenSuse
I'm no linux expert. In fact i'm kind of a linux newbie. My primary OS is windows vista, though my main work laptop is a macbook pro (running bootcamp / vista).
For the past several years I've toyed with linux — red hat, suse, and more recently opensuse and ubuntu (and it's kde based variant, kubuntu).
The latest revisions i've installed of ubuntu (7.10) and opensuse (10.3) were extremely impressive. Installed on a laptop, both detected/installed all my device drivers. A clean install, with no internet connection, successfully detected and configured my screen, chipset, trackpad, wireless and sound. Windows doesn't even get all those most of the time.
I've used ubuntu for a couple of years now, but a few months ago heard about OpenSuse. Some guy was giving it glowing reviews and comparing its ease of installation and use to ubuntu, so i thought I'd give it a shot.
Ubuntu uses gnome, though you can get a kde variant called kubuntu. OpenSuse also comes in both flavors.
I opted for the KDE flavor of OpenSuse, and i am really pleased with it. Ubuntu is great, but i don't think i'll be using it again any time soon. There's nothing extremely tangible that i can say i prefer about OpenSuse, but small usability touches and ui components make it my preference.
If you've ever wanted to try linux, now is the time. You can download "LiveCD" versions of both, letting you try out the OS without even installing it, just running it off a CD. If you like it, you just click "install" on the desktop to begin the installation process. They'll install boot-loaders if you prefer to dual boot.
Both Ubuntu and OpenSuse are suprisingly easy to install, have great device support, and look really good. You'll be amazed it's a free OS (OpenSuse looks especially polished). Transparency effects, multiple desktops, window switching, super-customizable desktop configurations and a whole lot more make both choices very exciting operating systems to tinker with. If it weren't for photoshop and a couple other presently-non-linux tools i still rely upon, i could easily see dropping Windows all-together.
Someday...

