Since this laptop comes with a very bright shiny display, one of your first problem after you boot your linux is too adjust brightness.
Doing some searches on google will reveal you a kernel module called sony_acpi which should make /proc/acpi/sony containing brightness and brightness_default files(these appear after you load the module) . Changing the value in this file should ajust the screen brightness, but on this FE21B model it seems not working.
After some more research(hours of trying and testing) I have found an application called smartdimmer, a NVidia specific utility which worked.
I assume it is not harder now to make FN+F5/F6 working, since one way or another you have now the control over your brightness level, but I haven't tried yet.