My desktop OS: Gentoo Linux
As a Linux newbie, Red Hat Linux 9 impressed me. When that excitement wore off, I jumped cold turkey into Slackware Linux. I tried Ubuntu but it was too slow for my low-end desktop, a 32-bit 1.58GHz Sempron 2300 with 512MB of RAM and no swap file. By this time I was a competent Linux user who enjoyed using the console. I wanted to go beyond distros designed to be user-friendly because I found them to be almost always slow on low-end systems. Gentoo Linux's speed, power, and many application and configuration choices made it an appealing choice for me.
Gentoo Linux is fast because every installed package is compiled for the user's hardware. Most packages are source code, but binaries are becoming more common and more popular, as they are quicker to install.
The Gentoo installation process was almost flawless; the exception was that I need the pci-utils package, but the Gentoo Handbook never mentioned the need to install them. I managed to get a response from someone on the #gentoo channel on irc.freenode.net who pointed me in the right direction.
Gentoo Linux is all about choices.