BSDF Shading is a separate and potentially more complicated subject. You can look under the mental ray documents for an explanation of what is built-in. It has some limitations and a couple bugs in 2011. You may also need SP1 to be sure it works. The built-in shaders are examples of what can be done rather than full fledged shading nodes. But with something like mental mill, you can begin making your own.
The built-in IBL is very much like environment dome lighting. It’s just smarter and easier to use. FG will add a secondary (or more) bounce beyond the direct environment lighting. Also, IBL at low quality generates grain instead of splotches (set to “light” or “automatic”) This is usually more acceptable for animation.
