Inherited CI 1.5.4: Rebuild or update?

[eluser]WanWizard[/eluser]
There are a few significant changes going from 1.x to 2.x, if memory serves me well.

Amongst them the change from Controller to CI_Controller (so change all your controllers), the change from "classname == methodname" constructor to using __construct(), etc.

Check the upgrading docs, and go through each one, starting with "Upgrading from 1.5.4 to 1.6.0". I'd expect you to be busy for a while, depending on the complexity of your application.

Also check anything third-party you may use, those need upgrading too.