Tiff as 32bit/c, seriously... (nearly) everyone in the VFX or Professional world dealing with HDR on a daily basis is using OpenEXR.
Well, I 'm glad they did not used the 4*8bit/c RGBE or ".hdr" (radiance) format, that would be really horrible.
I might sound not fair here, sorry about that, but when will Adobe arrive in the 32bit/c float age? With that I have in mind that everything, e.g., filters and tools, are able to work with 32bit/c float.
HDRI is certainly one of the most promising options these days. It is in use all over the place, but to work properly with it, 3rd party applications are needed, e.g. PhotomatixPro, which is great and I wonder why Ps or Lr misses out so many of these workflow option.
End of Rant
Sorry about that again, eruptions like that happen to me more an more, using Adobe stuff since 2 decades by now: I'm growing impatient ;o)