My sig rig, unit 1, is the workhorse for me. I analyze work data, write reports and prepare presentations (which I'm doing more or less right now, only taking a break). F@H 24/7 when I'm not working or playing (have folding set to idle at the moment) as my heart is in it. Gaming, surfing the web, do all my finances on it. Analogue to digital music. Some photo stuff, some benching. As I'm typing I've got 2 spreadsheets open, one word doc, a live connection to three work servers and OCF. Dual boot WIn7 and Linux, soon to be triple boot with WinXP. Gotta love unit 1 !
Unit 2 is the entertainment rig, an older 4200+ hooked up to the 42" LCD, Win7. My wife uses it for her surfing and socialization, photos, games, etc. Unit 2 backs up to itself and to Unit 1. Unit 1 backs up to itself and Unit 2. See a pattern here? She won't let me upgrade it only 'cause she thinks it's just fine like it is. Change scares her.
Unit 3 is a net book for the road, an MSI Atom. Really just for quickie communications on the road while at rest stops or hotel rooms, better than the Blackberry for the most part.
Unit 4 is not really a unit as such. It's a pile of parts that I scramble around for giggles. It's in the shop and is always semi-set up, semi-working, semi-taking up a large table. Linux.