For people who runs Ubuntu 10.04 LTS, this solution can still help.
Anyway, you have to know that Ubuntu 10.04 LTS (Desktop version only), 10.10, 11.04 and 11.10 are not officially anymore supported by Canonical.
If you're still using one of these, please upgrade to 12.04 LTS which is supported until April 2017.
Since 12.04 LTS, i don't need anymore to downgrade the kernel.
Just follow the official HowTo here : viewtopic.php?f=3&t=1091
About the packages to install, "samsung-tools" and "samsung-laptop" will be enough.
In case of a brightness control issue (FN-Up / FN+Down), this solution worked for me : viewtopic.php?p=5753#p5753