ok, there seems a bit of discussion about HDRI based IBL and indirect lighting solutions... There's a litte difference between the two which i feel i should point out.

IBL is image based lighting; Light cast in accordance to a the brightness and color of an image. For scenewide IBL such as in bryce6, the light will be cast from what is effectively a spherical dome around the entire scene.
Added benefit of HDRI for IBL is that there is a more then 256 degrees of brightness in the image used as light map, thus enabling you to create more realistic contrasts between for instance a sunlight and a lightbulb (both might look white to the eye but their brightness is difference).
IBL is not indirect ligthing, it doesnt calculate light bouncing off one surface onto another. Thus the light an HDRI might cast through the windows will not bounce around the room. So, as a result, the scene will not really benefit from it too much.

So as a result of this, which AS already stated, an interior render already has an environment for reflections etc. An IBL scene would mostly leave the inside of a room unaffected, after all, the walls and ceiling will obscure any light cast from the dome around your scene.
The only light from the IBL getting into the room would come through the windows. Once there, it will only be able to cast into a small part of the room because it won't create any indirect illumination yet. You'd need TA for that part of the solution. (or you could simulate it with textures and strategically placed light-sources)

An outdoore scene benefits from HDRI based IBL because there's light from the 'skydome' comming from all directions siulating light bounced off buildings and other objects surrounding your scene as well as sunlight diffused throughout the atmosphere and, being an outdoor scene, there's nothing to entirely (or at least mostly) obscure your image's subject from this light.

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