Session libraries?

[eluser]skunkbad[/eluser]
I really don't understand the value of using CI's sessions vs. standard php sessions. I am very comfortable using standard php sessions, and am not really fond of storing all session data in a cookie (encrypted or not). The user guide says, "The Session class does not utilize native PHP sessions. It generates its own session data, offering more flexibility for developers.", however the user guide doesn't specify what this flexibility is.

I'm probably going to extend the session class to use native php sessions, or include native sessions as needed.

One thing that is curious is that if I var_dump the CI session, even on a page load that had no previous CI session, the output of var_dump is a HUGE amount of data. Is this normal?