In short, I'm impressed. Granted, the last time Noise Reduction got any serious attention in Lightroom was about 10 years ago, so this sea-change is a long time coming.
I work in some flavour of Lightroom on every single photo I process, nearly every day. I'm a huge fan of the application, and not just because my employer is Adobe. But a couple years ago, I was forced to look elsewhere when it came to Noise Reduction - and Sharpening, for that matter. Prior to this Lightroom update I was forced to go to 3rd-party tools, such as Topaz DeNoise AI or Photo AI to smooth out excessively noisy images.
While I could get good results from these tools, I found myself tweaking the files before the final export out of Topaz, whether I needed to or not. There are lots of controls and options to play with in Topaz. I'll say this much for AI Denoise in Lightroom - it's easy to use. All you get for control is one slider. And based on the examples above, one slider is all I really need.
I've also read some comments about the time it takes to process the file as a new DNG file. I get it; we all want things in a hurry. But when I combine the facts that the effect is performed in-app and there are minimal controls to use, I think I'm actually saving time by performing this action in Lightroom, if all I need is to denoise an image. Going the 3rd -party route, I still have to invoke Topaz, wait for it to load itself and the image, tweak the image and then wait for Topaz to push out a final file, too, remember.
I'm sure this is also simply phase 1 of Denoise. I hope to see more zoom control (and a larger) Preview window, for example. I know we are working on supporting other file formats such as jpg. I hope that support extends to HEIC, Apple ProRaw and Tiff files, as well.
I hope this also signals that we're going to see some form of AI sharpening sooner than later. That would give Lightroom users the AI triumvirate; Super Resolution, Denoise and Sharpening. And then maybe...just maybe... I won't need to leave Lightroom at all.