I have 3 boxen at work. Two Dell P3 600's and a G3 Mac. Hardly pushing the envelope but as the development server is a 16 processor Sun box the desktop is not really a problem. The Windows box is mainly used for testing in IE and Eclipse (which I only use as a CVS client) plus stuff like Winamp and GAIM. The Mac is only used for testing IE Mac stuff and we are dropping support for that sooner or later. They share a monitor using a dual input switch but as we dont have a USB KVM anywhere handy there are separate mice and keyboards including a god awful puck mouse.
The linux machine is where I do my work. VIM (or several VIM's), and Firefox + Thunderbird and quite often the GIMP are open constantly plus about 3 or 4 terminal windows to different locations on different servers.
Its not a bad office. I traded in a lack of view from the window (which is pretty good as it looks towards the posh end of Bath over the river) for no one being able to see my screens. Handy that at times.