When I bring my Windows work laptop home, I can it and my Ubuntu laptop, side by side, from one keyboard/mouse. It's like having dual monitors, except with 2 CPUs and operating systems! I've also used it across 3 machines in the past.
Configuring a server in Windows is a bit counter-intuitive and klunky, but once it's up, it works well. A refresh of the config GUIs would be most welcome.
Ubuntu has a QuickSynergy GUI application that works pretty well, though I only use the Ubuntu machine as a client, so I can't comment on configuring a server.
Overall, this is a very slick and very useful application if you have 2+ machines that you'd like to have seamlessly work as one.
I used to use SequoiaView, but this application is better. It scans your drive(s) and builds a tree structure that lets you easily drill down to figure out what's eating your disk space. It also generates a treemap (I understand the term, but there's gotta be a better name- the visual looks nothing like a branched structure) that looks almost identical to SequoiaView.
The bottom line: This Windows application does one thing, show you what's taking up space on your drives, and does it very well.
The graphics are really amazing- probably the best I've seen in an open source application. And it runs on Windows/Mac/Linux (I've used the first two, so far...)!
I find the controls a little opaque, but I haven't spent a lot of time RTFM. My 5-year-old twins have recently developed an interest in space (they are upset at Michael Collins didn't get a turn on the Moon), so it's great fun to zoom around the solar system with them.
The Mac port seems a little unstable (it crashes from time to time), but frankly it's more stable than Google Earth has been for me.