You don't need to author all your assets in 'HDR format.' All that matters is lighting; you need to be prepared to set up your dynamic lights with values greater than 1.f, to be prepared to set up your texture-based lights (emissive materials) with values greater than 1.f, and to set up your skyboxes/reflection maps with values greater than 1.f. All the rest of your stuff stays exactly the same.
So it turns out I probably don't need those light probes after all. Oh well, they'll make good test art.
I wouldn't be surprised if it's not so true with games (which often cut corners for performance reasons), but in the scientific/visualization fields there are ways of generating HDRI textures for models so as to gain maximum quality.
I'm possibly going to be working on this for my final year project at the UofN this year.
The above image is one of the things a professor in CSIT did - the photos around the edge are of the classroom but with different exposures. All the different exposures can then be combined (not entirely sure how) into a single HDR Image.
From some of the stuff I've been looking at, it's still possible to get resolution/precision artifacts with HDR rendering in D3D9 - but I suppose they could be eliminated by using a technique such as that above. If we all had GPU's with terrabytes of VRAM [smile]
Jack