After upgrade, when to reboot or just restart X?

[T6]

if you update kernel and other tools you need to reboot so you can use what you just installed, even if you don't run a de

[cyrwyn]

I would like to hear from those who say that the DE is part of the operating system: Please tell me and everyone else just what specific files, i.e., drivers, libraries, etc., need to be loaded on a reboot after upgrade. I like to know exactly what's going on under the hood.

[T6]

i don't know the name of the files but must be the core files for kde4 and in a netbook all the modules talking to powerdevil and similar stuff that talks with kernel and with the hardware what requires the reboot

also the reboot is necessary to remember windows xp and the endless amount of restarts required, you can't leave all your past behind 

[Archie]

One such thing which are critical but does not require a reboot are the daemons although in some cases it is best to follow what is instructed. Check either the sound or video configurations. Log out or reboot.