Is there much difference between 1.3 and 2.1?

[eluser]talkingnews[/eluser]
I'm wondering if there's much functional difference between 1.3 and 2.1.

Because I see things in the user guide, like http://ellislab.com/codeigniter/user-gui...rence.html which says it's "Codeigniter version 1.3 quick reference chart". Is it still relevant?

I also see that the tutorial are grouped by <=1.7 and =>2.0.0 - but didn't I remember reading that 2.1 had some major changed from 2.0.1?

In other words, as a newbie, is the 1.3 quick ref and any =>2.0.0 tutorial going to be "safe" to follow?