Out of curiosity, what would be your advice for people who don't use El Capitan and don't have SIP?
(I disabled SIP approximately 30 seconds after installing)
Well I'd say be aware of what lower level drivers you install on mission critical machines, be sure that any Kexts you use are from reliable sources. And confirm that said Kexts will not cause system instability because of device conflicts.
For instance I installed an older version of a USB3 to Gigabit Ethernet adapter Kext and it would cause my multi monitor setup to lose connectivity after waking from sleep because the Kext interfered with an AMD graphics Kext. kernal panics would also occur because of this incompablity.
Kext Signing was introduced into Mavericks but was easliy bypassed by using a boot flag Kext-dev-mode=1, why Apple changed it is probably due to security. That part of the post was mainly for people to be careful when changing low level security settings.