A lot of that momentum comes from the fact that Linux is free.

There are a lot of people who've been able to ditch their Windows machines and switch over to Linux because they can now use their Exchange server for calendaring and collaboration from their Linux desktop.

Big Linux deployments have reached the point where it's become a real problem for administrators that they don't have nice tools to manage their servers and desktops.

Mac OS X isn't a free platform, and it runs on expensive hardware. It is not a plausible Windows alternative for our desktop customers, who are mainly large government organizations displacing Windows desktops and big enterprise corporations replacing Solaris workstations.

OS X is sweet: it's simple and intuitive, and I think GNOME shares a lot of values with it.

As a programmer, it's sometimes difficult to know how ordinary people with no technical experience are reacting to your software. Linux people tend to know other Linux people. In these usability tests, we selected test subjects who were experienced with Windows, but who had never heard of Linux, and asked them to perform basic tasks using the Linux desktop.