Mods, feel free to move this if there is a better home for this thread, I plan to post to it a couple of times over the next week or two in the hopes that it helps anyone who is trying to decide if DLO might be useful to them.
A summary of my initial conclusions are:
1. DLO is helpful for older lens designs that need some correction, and less helpful with lenses that are sharp and distortion-free out of the box.
2. DLO is a strong operator, it will amplify noise when viewed at high magnification levels, so other sharpening may need to be reduced.
3. DLO in DPP 4.x does not appear to increase the file size of the image like people complained about when it first arrived in DPP 3.x
4. While very slow re-drawing the preview on my whimpy laptop's CPU, really too slow for A vs B comparisons, you can change a setting and convert to jpeg just as quickly as before, so A vs B is easier done writing out several jpegs and then comparing the resulting jpegs.
5. I have not found a way to get it to happen in-camera, maybe just my bad, I'll edit this if I can find a way to make it work
6. It is possible that the reputedly strong AA filter on my 60D camera body will gain more improvement out of DLO than other camera bodies.
I have very recently found DLO within DPP, I use a DPP-centric flow so DLO should be well suited for me if it is helpful. I cannot compare DLO against PS or Lightroom so other people may find input on that comparison useful if anyone has a comment on it. I never found DPP's lighting optimizer to be very helpful, and I confused the acronym I suppose so I never realized DLO was a different product. Some experimenting this weekend taught me that DLO should be part of my flow for my EF 40f2.8 STM and my EF 100f2 lenses, but may not add much to my EF 300F4L IS lens unless I am using a very small aperture (rare on that lens).
As with most things related to sharpening, the use of DLO will be driven by taste, and will be traded off with noise tolerance, all of which relates to the viewing magnification. I typically try to stay below 50% magnification, generally if I am happy with an image's sharpness at 50% then I can make use of it for family and friends. The effects of DLO are more obvious at 100% or higher, but with the 40 and 100 mm lenses they can be seen at 50 and 25% magnification, which makes DLO useful to me. With the 300mm lens wide open, I cannot claim that I can perceive a change until I get to 100% magnification, although I plan to experiment with small aperture settings. In reviewing old threads on DLO, I found a lot of wishful thinking in 2012 when it first came out claiming its deconvolution might be nearly perfect, but convolving any kernel into noise gives creepy artifacts under high magnification. I'm an engineer, not a scientist, so theoretical perfection isn't as interesting to me as "is it helpful?" so here we go with some experiments.
A link to a couple of 100f2 examples are here in the macro talk thread, at 100% so you can see an example of added noise in the DLO at 80% example:
I will add more posts with examples over the next couple of days.