We recently got a 4.5mm fisheye lens (for APS-C) in the studio for getting HDRI information when we are out and about on shoots/location. Creating HDR/lightprobes this way has many advantages both cost wise and practically.
Spheron cameras are in my opinion - the most overrated, slow and overpriced pieces of crap that people think you have to use to create an HDRI.
OK, its somewhat automated and accurate - but its slow and its a big bit of kit to drag around and you almost dare not touch it because it cost so much. You can get just as good results with a DSLR and a fisheye.
Lets think back to the early days of high dynamic range light probes. They worked and most were done by taking photographs of a polished chrome ball, ball bearing or in my case....a crappy Christmas decoration ball. As long as you captured the light intensity - it was fine.
Being able to use 180 fish-eye lenses, unwrapping them and stitching them together in 15 mins with something like PTGui is awesome. Plus you are shooting RAW on the DSLR - so you can get HUGE resolution and detail. I shot 6 sets of 7 ev exposures on a Canon 550d.
Here's an HDRI of my messy kitchen that you can download and use for whatever you like.
The 3k map you should use for reflections and the small convolution map you should use in the skylight/dome-light slot for optimised light sampling and faster renders.
Heres a simple test render of some good ol' teapots using this HDR