I use one on a Sony A55 crop sensor. Check my username on Flickr (rtrski, same as here) for example shots. I leave the EXIF in all my shots so you can verify settings that way as well as whether the particular shot has been cropped by the pixel count.
A couple of my personal favorite examples - not necessarily the sharpest focus on the main subject, just the overall field of view etc. (always would like to make the shot perfect, but of course never do). Note also that I'm shooting with a custom minidome by Underwater Camera Stuff (uwcamerastuff.com), so take that into account when judging corner sharpness. I could get better with a big 8" dome, certainly...but I just don't like travelling with those.
Selected faves are more or less in reverse chrono order (latest first). At least one is a 'CFWA' type shot - the dome was almost touching the scorpionfish, maybe 3-4cm clearance maximum (I eased in slowly so it didn't bolt).
Remember that the 8-16 has a domed front element, so you cannot use diopters or filters on it - you need to make sure your dome alone gives you the corner sharpness you're after. The front element moves a little bit across the zoom and focus range, but not much, maybe 1cm travel total. I'm also very pleased with this lens above water.
Current rig: Sony SLT-alpha55 in Ikelite housing, Sigma 105mm f2.8 DC Macro w/ Ike 5505.58 flat port or Sigma 8-16mm f/4.5-5.6 DC HSM behind UWCamStuff custom 5" mini-dome. Dual INON z240 Type IVs triggered with DS51 for TTL mimicry, or DS51 alone with home-made ringflash assy for macro.
Topside, unhoused: Sony SLT-alpha99, Sigma 150-500mm + 1.4TC, Sigma 15mm diagonal fish, Sony 24-70mm f2.8 CZ, Tamron 180mm f2.8 Macro...all the gear and nary a clue...