Some feedback from a long-time Lightroom user:
Nikon "High-efficiency RAW" support is missing. This is IMHO the fault of Nikon and their vendor TicoRAW. If you're going to come up with a new RAW format, then it is your responsibility to commit the decoder to open-source libraries! Sure, patent and license the encoder, but if you keep the decoder closed-source and proprietary, then you're a .
The installer is an EXE instead of an MSI. Publish an MSI! Use the "wix" tool in your build pipeline, it's not that complex.
The installer and the deployed app are not digitally signed, which throws up a litany of scary warnings and errors. Other open-source developers have gone to the effort of signing their builds.
On first launch the app flashed a command-prompt window up and then disappeared.
The "Exposure" tool has an automatic setting to compensate for the camera offset. Okay... then why did I bother to offset the exposure just to have ansel undo my intent by default? Then... it layers on a default +.7 EV for like no reason...
The overall GUI is completely non-standard and bizarre. I've never seen anything even vaguely like most of the UI controls in this application anywhere else... ever. It's like someone who's never seen a GUI in their entire lives invented everything from scratch.
The non-standard UI elements like the combo boxes aren't just weird, they're buggy too: they don't work consistently with the mouse. I can see the option being highlighted, I can click it... and then it'll pick something else! They only work reliably with the keyboard. In general the "selected item highlight" appears to be off-by-one, but not consistently. It's bizarre.
Colour management is a mess. On a HDR OLED monitor, Lightroom can display wide-gamut and HDR images correctly if the desktop is set to HDR. E.g.: if toggle an image from SDR mode to HDR mode then the only difference is that highlights get brighter and some extreme colours become more saturated. Everything is correct by default and SDR tones don't "shift". In ansel, the colours look wrong and any setting I choose in the menu makes them even more incorrect.
There's a lot of talk of HDR support on the site, and the menus even "suggest" that PQ/HLG support is there... but not really. The export formats are all from the 1990s and modern HDR formats like HEIC, AV1F, JPEG XL, etc... are missing in action.
A lot of the options/alternatives seem like developers being too reluctant to get rid of old, bad code. For example, if a new superior demosaicing algorithm is added, then it's usually best to just drop the worse ones! I tried every option available, and all but one was broken, to the point of returning super-green results or just all-black. Lightroom for example just uses a really good demosaicing algorithm and doesn't burden users with a choice of a bunch of bad alternatives.
In general, the same criticisms apply to ansel that applied to Darktable: over-complicated, too many options, most of which are either wrong or useless. Internal details exposed to the end-user in the UI that should be debug traces for developers, not permanent GUI elements. Easy to inadvertently "break" the whole thing by reordering pipeline elements by dragging and dropping something accidentally.
I suspect that on top of the ~30K lines of code Aurélien Pierre deleted from Darktable 4.0, another 60K should be deleted...