if I buy an ultrasonic cleaner for my records will I be able to hear the difference?

I suggest you take a few of your recently-cleaned records to a dealer who sells ultrasonic cleaning machines, and have him clean them for you. Then you can decide for yourself.

For me, the appeal of ultrasonic isn't just cleanliness. It's the one-button "set it and forget it" convenience that something like the Klaudio offers.

While I echo @cleeds observations regarding convenience for me the real benefit of the us cleaner is how it improves the detail and resolution in LP playback. I used to own VPi and ClearAudio vacuum cleaners and the best thing these did is clear the record. My KL Audio actually changes and improves the sound of the LP, even those that play and appear clean. Whether this benefit is worth it on your system is for you then decide but the investment you make now will pay back as your system improves 

Results will depend on the condition of the record.  Do you buy a lot of used vinyl?

I know you are looking for input from people who own an US cleaner, but that said, cleeds post makes a lot of sense!

(I've ordered the Degritter US cleaner, hopefully to arrive this fall, and I'm really looking forward to trying it out.  It will be my first record cleaner, beyond using an anti-static brush).