I replaced the harddrive that came with the system with an SSD containing my Linux installation (currently OpenSuse 12.2). However, you can make it work (at least I can, on my Satellite P750D) with some trickery.
The keyboard backlight is initially on when you turn on the laptop (if enabled in BIOS), but if you have ACPI enabled it normally shuts off as soon as you start to boot into Linux (immediately after the GRUB boot screen). Here's some more details on the problem and a hardware workaround. Meanwhile, the bug is definitely not fixed.