robert_love recently wrote that book on the Linux kernel and now works for Ximian/Novell, where he is charged with doing the kernel work needed to make the desktop work. Recent posts include a screenshot of GNOME interacting with hotplug+DBUS.Now that I look at that picture: I got a digital camera for christmas. The possibility that it wouldn't work from Linux didn't even occur to me, but thankfully gphoto worked without any trouble at all. I did have to discover the Linux 2.6 secret mounts:
mount -t usbfs none /proc/bus/usb
mount -t sysfs none /sys
I haven't tried the hotplug stuff yet, but I don't think it's useful until the userspace stuff is finished.