Here is a quick tutorial showing you how to use the new AI denoiser coming out with Blender 2.8. I show an example of the AI denoiser being used on one of my animated scenes.
I've seen huge increases, turning 66 hour renders into 45 minute renders on a single machine. Of course, there are some limitations. It only looks at one frame at a time - so the denoise can cause distortion in animation. It sometimes gets a bit fuzzy with edges, so maybe not ideal for architectural renders, at extremely low samples.
For client work, I would be wary, but for internet compression, I think the results are adequate and as long as you crank the samples a little higher - it is a great tool. Also, if you're on a lower-end machine it's better to be able to render something than nothing at all sometimes!
Watch in 1080p so you can see the visual difference better. Share any of your creations, I would love to see. I really do think that Eevee and AI denoiser make it easier for people to create renders with less powerful computers, which is really awesome.