Another convert here. I have a 10L 40hz tank and a Vinyl Stack 3 LP combo. My process is:
Spin Clean to remove surface / loose debris and pre clean
Blot
US Clean using Rushton's formula at 35c. 1/3 RPM; 5 revolutions in 15min
Rinse
Nitty Gritty Vac Dry
My findings match most experiences. Clean LPs often exhibit a noise floor lower than that of my system. I hear much better transient response, and extreme HF. I hear much more air and space around musicians.
My take is that over time, a layer of dirt bonds to the groove surface walls. This layer is probably only a few microns deep, but it is enough to blunt the leading edges of transients, mask extreme treble extension, and the very low level audio cues that allow us to "hear" space. This layer is generally impervious to scrubbing. A US session removes this layer, exposing more of the very subtle modulations deep in the groove.
Regarding surface noise, even previously cleaned LPs exhibited a shhhhh-woooosh sound in the background and between grooves. After US cleaning, in many cases this sound is gone, and is replaced by silence.
On the other hand, surface damage is now more easily heard probably because the scratches are also cleaned of smoothing junk etc and the rest of the LP is now more quiet.
I have run into an issue where I hear more tics pops as I get closer to the label. I increased the amount of fluid in the US tank, and more carefully vac clean, which seems to have taken care of the problem.