The below is for 9.10, So these options may have been improved in 10.04. I
have not checked yet.

I have the satellite L505. I assume the 550 also probably uses the insyde
h20 BIOS, which breaks the already limited acpi support we had for
toshibas. Getting the fan to work was a small miracle... and none of the
function keys are supported... touchpad must be turned on and off using
"sudo modprobe -r psmouse"... if wireless or mouse is turned off with
function key in windows, there is nothing short of God intervention that
will get them back on in Ubuntu w/o rebooting into windows and turning them
back on... That is the only thing keeping me from stripping windows from my
pc and basically leaves me with a wasted partition. Partial fan automatic
fan control is achieved by inserting acpi_OS=Linux to the appropriate line
in grub and installing lm-sensors. The only remaining issue with fan is
that I have not figured out how to get variable speed to function (it comes
on at a medium high speed) nor how to change the on/off setpoints. I
suspect both of these might be addressable with the proper changes to the
sensors3.conf file. Resuming from suspend is also fickle... but never
involves much more than switching to alternate tty and killing
gnome-scrensav. Occasionally fan will not turn back on after resuming from a
suspended state, requiring a reboot.