it depends, you can if you want to and it may speed up some programs but alas it may also slow way down others and or crash them.

ie: just make sure your ready to risk a loss of either a program or your system, however do not stop it when u first prelink.
edit: oh! and if you do prelink make sure you keep custom system mods to a minimum - ie: source packages, etc.. or else you may have to re-install ubuntu, etc...due to a crash/lockup, etc..