[eluser]Phil Sturgeon[/eluser]
Fight fight fight!
CodeIgniter 2.0 makes no change to the way in which the core libraries handle errors as that would break apps horrendously and require developers to review every line of their code to update.
You should consider 2.0 as more of an update. It is 99% compatible with your existing apps, with the main differences being no more plugins, and the renaming of the Model class to CI_Model.
Upgrading is a 5 minunte job for most apps and I doubt any of the guys at EllisLab will want to change that. Remember, EE2 runs on CodeIgniter and fundamental changes to error handling in CI would add a lot of work for the development team.