"The most" is a difficult answer. I guess it depends on what I'm doing. I have a small custom-built NAS/backup desktop that runs FreeBSD, and has XFCE4 on it, my little girl has a repurposed Macbook Pro that runs ArchLinux with KDE, my wife's laptop is Windows 8, and my desktop system dual boots FreeBSD with KDE, with Windows 7.
Information about the backup? Well, from about June until now, my main desktop has had a fried video card, so I connected the FreeBSD box to my monitor, and used it. I wound up putting XFCE4 on it.
Once I got my other machine running, I haven't really touched it since.