I used an ultrasonic cleaner on my brass all last Summer. I liked the results that it gave, especially the clean primer pockets.
But, I have never experienced difficulty seating bullets due to having brass too clean, if there is such a condition. I know the folks on 6mmbr.com reported using some sort of dry lube on the inside of case necks to aid in bullet seating.
I personally use Citranox as a cleaning detergent, works fine. Right now I need to be looking for a new U.S machine, since my went kaput.