What should not be installed in the /Extra/Extensions folder?

[vinnie881]

I want to keep my system as vanilla as possible, but I am not sure if I should keep EVERYTHING in the extra folder, or if certain items it's ok to install to /S/L/E

For instance I have a specific kext/driver for my network card.  Should that be installed in my Extra/Extensions folder? 

I am just trying to figure out what items I should not put in the /Extra/Extensions folder if any?

Thanks!

[Gringo Vermelho]

It depends.

The main reason for placing kernel extensions in /extra/extensions is to keep them safe from getting overwritten by Apple system updates.

If you're using a kernel extension that doesn't replace an Apple kernel extension you can install it in /S/L/E/ without having to worry about it getting overwritten during a system update. AppleVIAATA and skge.kext (Marvell 61xx PATA controller and 88SE8001 LAN) are two such drivers.

Unless you use a .plist only (aka "legacy") kernel extension you can't normally use a network driver from /E/E because of dependencies (IOPCIFamily and IONetworkingFamily). You can check dependencies by looking at the end of info.plist inside the kext.
A workaround is to place the kexts that your driver depends on inside E/E as well - but it's ugly and it will get uglier still when those kexts get updated by Apple - the system will reject the older versions in E/E and load the updated ones in /S/L/E.