Certainly.
How does EE 2.0 work with CodeIgniter?
http://ellislab.com/blog/entry/expressionengine_20_fully_codeignited/
It is just like any other CodeIgniter application. It is built on an essentially stock codebase of CI 1.7.1
How will CodeIgniter integration benefit us?
Also well answered in the link above, but the crux is:
If you’re an ExpressionEngine developer you will have a greatly expanded community of talented developers working with you, and for you.
If you’re a CodeIgniter developer, this means you can drop a full-fledged content-management system right on top of your existing code base, and have it work.
Here are a few other nice things that we’ve shown.
http://ellislab.com/blog/entry/accessories_a_quick_primer/
http://ellislab.com/blog/entry/site_themes_in_2_0/
http://ellislab.com/blog/entry/a_present_for_your_friday/
How will 2.0 help us build better sites and attract better clients?
Allow me to expand this question to “better sites than EE 1.6”. The answer is, it won’t. ExpressionEngine will remain among the most flexible platforms on the planet. Anything you can do in EE 1.6 can also be done in EE 2.0. The principal gains are to the backend, where the CP is better organized, faster, more flexible and more powerful, as well as access to a broader community of third-party developers; but in terms of actual “will I see a difference on the public facing part of my site” the answer is essentially “no”.
We’re replacing an older engine with a shiny, modern piece of engineering, but the car will still look the same to those not looking under the hood.