Today the official site for Tom Clancy's Rainbow Six: Raven Shield is updated with some q/a from Raven Shield's Art Director, Carol Bertrand. Here is a clip:

Q: You used the new Unreal Technology to develop Raven Shield. What does it allow to do in terms of graphics? What are the strong points? And the challenges?

True, we are using the ever-evolving Unreal technology. I say ever-evolving cause one of the biggest challenges is to keep up with constant changes made in the toolset. It's also true that UnrealEd is not exactly made for our needs, so we have to do our own modifications in the tools some times. On the other hand, we have a state-of-the-art technology that allows us to display a lot of stuff.