kernel mode safe or not ?

It looks like this is a stability option. In searching the gaming sites there is apparently a lengthy tooltip visable when hovering over the choices. the gist of which is:

User mode gives the best monitoring performance and doesn't consume kernel address space, while Kernel mode can protect hardware-mapped memory ranges from unauthorized access by badly-designed applications* and in this way can protect the system from instability.

The Afterburner changelog for 2.2.0 Beta 9 states

Added new compatibility option allowing using protected kernel mode low-level access to hardware instead of user mode one. This option can also be used to bypass Punkbuster related stability issues

Punkbuster

PunkBuster is a computer program that is designed to detect software used for cheating in online games. It does this by scanning the memory contents of the local machine. A computer identified as using cheats may be banned from connecting to protected servers. The aim of the program is to isolate cheaters and prevent them from disrupting legitimate games.

http://en.wikipedia.org/wiki/PunkBuster

This is apparently safe, and suggested for people with instability or BSOD issues. A Guy