What is considered "acceptable" is a very subjective thing. What one person considers fine, another person might find very objectionable.
I have the split mono-leafs and CalTracs on my Mach 1. In my opinion, they do make the ride considerably harsher, even backed off on the engagement point. Adjustable shocks do help, but only to the extent of how much bouncing goes on after the initial shock of a bump or dip. In my case, I found double adjustable shocks were much better, being able to control extension and rebound. I switched from the standard Calvert shocks, to QA-1 double adjustables. Still, it's not anything close to what you'd feel on a stock type suspension. Stiffer springs are just part of the deal, and there's no way around the fact that it affects ride quality in a negative way. If you used soft springs with the Calverts, you're still going to get some wrap up between the roller and rear axle mount, which is kinda defeating the purpose of having them in the first place.
Having said that, I can live with them just fine. I don't mind the harsher ride, or the occasional noise from the roller contacting the springs. But the car is pretty noisey anyway with a roudy cam, headers and Borla mufflers. Performance muscle cars are supposed to be noisey though.