Gaming Illustrated has conducted an interview with Interplay's Chuck Cuevas, talking to the producer about various aspects of Fallout: Brotherhood of Steel. Here's a little something to get you started:
Q: How will playing as a different character change the gameplay experience?
A: Each of the player characters possesses different starting strengths and limitations. Nadia, for instance, is very mobile and excels in the use of ranged weaponry (can even use dual pistols), but can't use some of the really huge weapons. Cyrus, on the other hand, hits hard in melee combat and can haul around a 200 lb gun, but isn't as quick on his feet, nor is he ambidextrous.
The cool thing is that, even after you choose your base character, you can develop that character any way you want by building up experience and applying that experience to your skills. All of the characters have general skills for the player to improve, but each of them also has unique skills. For instance, Cyrus can improve his combat efficacy with home-made weapons using the (Wastelander) skill.