It is laggy to the extent where a normal workflow is not possible any more.
Using an 8-core AMD 3.1Ghz, with 16GB of RAM and an Nvidia GTX960 under Win10 64bit.
Switching between photos in the Develop module, even when Smart Previews have been generated. I've even changed the standard preview size to a size smaller than my 4K monitor. Happens on my Fuji XT-2, XPro2 RAW files (compressed) and Fuji jpegs. Haven't yet tested my Canon files.
Slow previews when scrolling over presets. It used to simply preview in the navigator window, but now it previews simultaneously the on-screen images at preview-size which makes everything reaaaaalllllllyyyyy slow. I don't like this feature but can't find a way to turn it off.
Pasting copied settings. Too much delay now.
I've since rolled back to 7.2 until these performance issues are resolved.
i7 4770K, 32GB RAM, Win 10 64, GTX 1070 8GB card, 4K monitor.
I got Lightroom 7.3 to make a pano from 10 vertical D800E images - this it did without too much of a sweat, and the result is a DNG at 33,300 pixels and 970Mb.
If I try to add even a graduated filter to this not-so-massive DNG then the Dev module crawls to a halt - just placing the filter takes nearly 2 minutes of spinning progress indicator.
If I close Lightroom and open the DNG in ACR, then I can apply any adjustment I like and there is no slowing down of anything.
So why would ACR act normally and the Lr7.3 dev module act like it's been shot with a very big gun??
Today it was so particularly slow for me that I had to record a video
Its so unusable at this point that I'm wondering if I should ask for a refund until they find a solution.
Sorry for the poor quality, I had to record with my phone as screen recorders wouldn't work with lightroom sucking up all computer resources.