They work really well with the coils on my 2500. I don't notice any difference unloaded but they firmed up the ride nicely when we're pulling the fifth wheel. There's probably a 1/2" or a bit more of a gap unloaded. I've had them on for almost 5 years with no issues, and obviously they're zero maintenance.
Most of the complaints I've read on them are from guys with half tons, and I could see them impacting the ride more with a softer suspension that would let the axle slap into them harder. I think I paid under $200 for mine on etrailer.