Like you, I’ve used Adjust AI on a range of images, and the results have been mixed, some good, some less so.
The images I used were all JPG’s, from four different cameras, a Canon Powershot G2 (2272 x 1704px), a Canon IXUS 110 IS (4000 x 3000px), a Sony SLT-A57 (4912 x 3264), and a Samsung S8 phone (4032 x 3024 px). All were sRGB colour space and all had no previous processing done to them.
I didn’t find processing time to be a problem (Windows 10, 16GB RAM, i7 processor, GTX 1050ti Graphics card with 4GB memory), but your images may have been larger.
In Adjust 5, which to my understanding Adjust AI now replaces, there are as I see it basically two modes of use. The first is to hit the reset button, then manually set the sliders until the image is to personal taste, and not make use of the the presets. The second is to run through the presets (someone else’s choice of settings, or settings you have previously found worked on another image) until a preset is found that gives what you are looking for, or at least close to it. Probably more often than not that preset becomes a starting point, and the sliders are then used to fine tune the result.
Regardless which of the above methods are used, whether the end result is considered good or otherwise is somewhat subjective, because the image has been adjusted to personal taste. What I think looks good may not be seen as such by others, and vice versa. Some users might be processing to make the image more like they remember the view when they took the photo, for others it might be to make the image pop or look more HDR.
With Adjust AI, one can still opt to hit the reset button, leave the Auto Adjust AI option OFF, and adjust the sliders manually to adjust to taste, but in this mode it does seem to lack some of benefits of Adjust 5’s “adaptive” controls.
In my tests, I was looking to leave the manual sliders alone, let Auto Adjust AI on its Standard setting adjust the image to it’s “AI taste”, then see whether that came anywhere close to my taste. I should state here that I try to have images reflect what I remember seeing when I took them. I personallly am not a fan of HDR images, and pop for my taste has to be quite mild.
So to my results using Adjust AI.
I found some of the images I processed using just Auto Adjust AI were both an improvement over the source image, and quite acceptable without any further changes.
A further, larger number, were able to be made to suit my taste after using Auto Adjust, by simply reducing the strength where Adjust AI was being used freestanding, or reducing the layer opacity when used as a plug in from Affinity Photo. The reductions needed varied quite widely.
Some processed images did appear to me to be over saturated after Auto Adjust AI, but I was generally able to resolve that with just the saturation slider in Adjust AI.
In some cases Auto Adjust AI appeared to produce a colour cast. For example, a few beach scenes needed some positive colour temperature adjustment to overcome the introduced bluish cast.
I also had a couple of beach scenes where I thought the Auto Adjust AI handling of the sky and the sea colours was quite good, but some of the brownish rocks in the foreground became too orange for my taste. It would have been possible to correct that by a significant reduction in setting of the strength slider, but at the expense of the improvement the AI process had made to the rest of the image. It was better left and subsequently corrected using the HSL Colour tuning in Topaz Studio.
Given the wide range of personal tastes, and the wide range of images, it’s hard to see the Auto Adjust AI process on its own being able to satisfy everyone all of the time. For me, fortunately most of the time so far Adjust AI has produced at least a pretty good starting point quite quickly, and with a few exceptions it has then not been hard to get from there to a suitable end result.
I see myself using Adjust AI for most instances where I previously have used Adjust 5, but I will keep Adjust 5 to fall back if I need to.