to buy or not to buy (ultrasonic record cleaner)

You can manually clean pretty effectively without spending a lot of money. One of the issues isn't just whether the chemistry is effective, but how easy it is to remove from the record without leaving a residue that includes the chemistry plus contaminants.
Rinsing is good. But dishwashing detergent is pretty heavy. Dawn was popular with car detailers to strip off wax build up before they would get to work on a painted or clear coat surface. It has a lot of stuff in it that you don't need for cleaning records. Cheap yes. I think you can do better without spending much more.  

Here's the 2nd Edition of Neil Antin's Precision Aqueous Cleaning of Vinyl Records. It expands on the chemistry and processes, and includes a much expanded section on ultrasonic chemistry and processes. Not a light read, but an excellent reference. It is a free download. Neil did all the work; I just published it. 
https://thevinylpress.com/precision-aqueous-cleaning-of-vinyl-records-2nd-edition/

@whart 

Thanks. Will curl it out. 

For those that already have extensive experience with an ultrasonic, is there any prep you do prior to use?  Visual inspection for any blemishes or material that probably should be removed with a fingernail or something?

I bought some used ones the other day and ran them through my (admittedly low-end) ultrasonic and they are pretty clean and shiny now, but, I found the cleaner won't get rid of things like the chunk of chewing gum (small, almost not noticeable) that some prior owner left deposited on the vinyl. 

Of course they also don't seem to be able to clean up 100% (although considerably) the results of many many abusive plays over the years by owners who had probably played them on groove-grinder turntables with dust all over the stylus and/or coin taped on the cartridge head to keep the needle in the groove.  The LPs quiet up considerably after a clean in the ultrasonic but can never be made perfect again if they have been damaged, at least in my opinion. 

I preclean any used album and some new ones. Ultrasonic is good at the fine cleaning but the basic stuff I do manually via a Monks Omni. At the same time, I inspect the record-- Neil got me onto using a UV light which is instructive, but not all telling. What you can see is some particulate and differences that aren’t as visible in normal light in the vinyl itself- not that there is anything you can do about the latter.
Given how the Monks works, if a record has a warp, you will know it. In those cases, after a preclean, the record will go into an Orb made DF-2. Final cleaning via US (currently using the KL which is hanging in there). I rinse, using high grade water, a vac dry on the Monks. My set up is shown in my system photos on Audiogon, but I’ll include a shot here: https://thevinylpress.com/app/uploads/2017/12/DSCF0766.jpg