We tested openSUSE, Ubuntu 8.04, PCLinuxOS, Mandriva Linux One, Fedora, SimplyMEPIS, and CentOS 5.1.
Each of these distributions was installed on five machines:
* Homebrew AMD (NYSE: AMD) Duron 1.1-GHz processor; 1-GB RAM; 80-GB hard disk; Geforce FX5200 128-MB AGP graphics.
* Lenovo Thinkpad T61 notebook computer; Intel (NSDQ: INTC) Core 2 Duo 2.2-GHz processor; 1-GB RAM; 80-GB hard disk; nVidia Quadro NFS 140M graphics.
* Sony VAIO TX series notebook; Intel Pentium R 1.3-GHz processor; 1-GB RAM; 80-GB hard disk; 1366 x 768 widescreen display; Intel 915GM integrated graphics controller.
* Dell (Dell) XPS 420; Intel Core 2 Quad 2.4-GHz processor, 3-GB RAM; 160-GB hard disk; 1680 x 1050 widescreen display; ATI Radeon 2600 HD 256-MB graphics.
* VirtualBox virtual machine with 1-GB RAM and 128-MB video running on Dell XPS 420.
Even if some of the distros shone brighter on the whole than others, most of them did fairly well -- and all of them had at least one truly outstanding feature that might be the deciding factor for you. I should also note that many of these distributions either have commercial support options (like Ubuntu) or full commercial versions (openSUSE) available, in case you want to graduate to something a little more aggressively supported.