Ever since it was announced that ExpressionEngine 2.0 would be running on CodeIgniter, the forums have been jammed full of "CodeIgniter 2.0" questions. I have answer this so many times I wanted to clear things up. [...] I figured, instead of just ranting about it, I could use this oppertunity to discuss what is, what is not and what should be going into CodeIgniter over the next few versions.

He breaks up things into four categories - confirmed features, missing features, minor syntax changes and a "crazy but helpful" section.