LP's... Do they sound better now than 30 yrs ago?

@markmendenhall - there are plenty of threads here and on other fora that sing the praises of US cleaning. I've owned both the Audio Desk and the KL. But, since I'm buying a lot of old records, particularly UK and EU post psych stuff, circa 1967-71 or so, I need the ability to clean out groove grunge that, in my experience, ultrasonic alone doesn't always effectively accomplish. I use US cleaning in combination with a vacuum machine, and for problem records, use a fairly strong cleaner- AIVS #15, followed by a pure water rinse. My next ultrasonic will be a DIY, because it offers more flexibility.  Many of the DIY US adherents get in way cheaper than the made for LP machines, but I'm after the feature set and flexibility. I use a point nozzle type vacuum machine, which doesn't have some of the issues that the more conventional wand type vacuum machines do. Rushton Paul wrote what I think is a seminal article posted elsewhere on this site, synthesizing his learning from a very lengthy thread on DIYaudio on US cleaning machines; he also experimented with filtration, a pump, and chemistry (the surfactant that breaks surface tension of the water and enhances cavitation). Well worth reading in my estimation. 

Thank you whart, so if a good scrubbing using a VPI 16.5 for example results in a an improvement in album playback from a zero (very dirty album but one in good condition otherwise) to a 6.5 or 7 on a scale of 1-10, where does the needle move towards a perfect 10 using a good ultrasonic cleaner in addition to the mechanical cleaning?   

Do not scrubb - soak with good fluid, you are pushing dirt deeper into the groove.

Bill, I propose an experiment. I will send you one record that I cleaned on Okki Nokki machine with Audio Intelligent fluids. Listen to the record, then clean it using your usual ultrasonic plus vacuum cleaning routine, and listen to it again. Then send it back to me and I will listen to it. Then we'll compare notes. This should be interesting. Your system has much higher resolution than mine, but what I have is very sensitive to small changes. I have two copies of the record I would send you, exactly the same pressing, so I would be able to directly compare.

@markmendenhall - it is less scrubbing, and more agitation. My method, for problem records, is to pre-clean a dirty record first using a mild fluid like the Hannl, that doesn’t require agitation or soaking to remove as much of the particulate matter from the record as I can by vacuum without agitating and soaking. This reduces the risk of grinding particulates into the record that @Inna mentioned.
Everybody has their preference on methods, but I then use a Lloyd Walker applicator, which has a directional fiber to apply the AIVS # 15. I will use a fairly liberal amount, and agitate while the RCM platter is spinning. Then, i’ll shut off the motor and continue to agitate, adding more fluid. My soak times vary, depending on the condition of the record. 5-15 minutes. Eventually, I’ll add even more AIVS # 15 and vacuum it off. Then do a rinse with high grade lab water and vacuum.
The ultrasonic adds a different kind of cleaning and can help loosen some of the stuff that brushing can’t- the bristles or fibers in conventional record cleaning brushes aren’t really fine enough to get into the grooves. Those Disc Doctor/MoFi types are good to evenly apply the fluid but they don’t work as well on the Monks given the speed of the platter and the lack of a clamp. Sometimes, I’ll pre-wash, using the above methods, rinse, vacuum, pop into the US for a wash only and vac dry. If the record is still a problem I will reclean using the AIVS # 15 and will be a little more aggressive --not scrubbing forcefully, but agitating vigorously.
I’m not sure I can say that the results are consistent- some records clean up from distorted to silent players with no groove grunge. Others require little to get them to play quietly. And some are a lost cause. I don’t deliberately try to buy bad copies on the cheap. But some of these records go for well over $500 in "VG+" condition-plays with crackles. A mint copy is often over $1,000. So trying to find something that is closer to mint in condition and cheaper than VG+ with crackles is the goal. These kinds of records are worth the trouble because the reissues generally sound like crap (assuming there is a reissue and are themselves not plagued with "new record" problems in manufacturing and handling).
I rarely encounter a perfect record, but think about it- short of an unplayed copy that wasn’t damaged back in the day in manufacturing or handling, how many 40 or 50 year old records do you encounter that are "perfect"? My standards are high- I don’t want clicks, pops or distortion.
New records, badly manufactured, can have similar problems that often aren’t fixable- non-fill or stitching, where the melted compound hasn’t flowed evenly in the grooves; scuffs, which are sometimes only cosmetic and some that are noticeable scratches- those don’t get "fixed" by intensive cleaning. I can flatten a warped record with about an 80% success rate using a larger Orb/Furutech (some people get great results with a Vinyl Flat for a fraction of the price, but it is, in my experience, a more time consuming process). I get off center spindle holes on new records as well as older ones.
To me, every record is different, and that’s why i’m reluctant to say you’ll go from a 6 or 7 to a 9 on a 10 point scale. A 7 would be unacceptable to me. A 10 (which is the rare bird and is usually an old record I’ve owned since new or the lucky unplayed copy from 40 years ago- not ’looks unplayed’ but actually never played) is pretty rare when you are buying old scarce collectibles. I’ve encountered very few of those.
I’ve had several situations where I’ve bought multiple pressings of the same record simply because the copy doesn’t meet my standards. (Even the Mint- ones are often misgraded or warped).
It is a flawed medium in many ways, but it really does deliver the goods if you get a well recorded record in great playing condition that you enjoy. So, I’m cautious about overstating the benefits of cleaning, but at the same time will confidently tell you that where I have a problem record, I can often improve playback quality by using multiple cleaning methods and repeated cleanings.