My main workstation is rigel. It's a Sempron 2800+ (1.6GHz), 512MiB RAM, w/a GeForce4 Ti/4200. It's running a tuned install of Slackware 10.1, soon to be upgraded to 10.2 when I get around to installing my new 160GB drive. I love this machine. It spends most of the time with the FPS railed, and never drops below 85, even when there's tons of action.
My other machine is yzceti. It's an IBM Thinkpad w/ a 750MHz PIII, 128MiB RAM, a 20GB HDD and a Mach64 based video card. The screen is locked at 1024x768, so Trem doesn't run well at all in fullscreen mode. However, I primarily use the laptop for mapping, which it is fine for (particularly since I turn the texture quality down to flat shade in GtkRadiant--I do the final texturing and touch up work on rigel, which is more than capable). yzceti is running Slackware 10.2 (rigel was upgraded from an older machine, and the old harddrive had 10.1 installed on it).
Jeff