Does anyone have any hands-on experience with the Mr Pex RetroPanel? I am curious about their floating floor concept, level floor tolerance on existing concrete, joints/seams reflecting through in the carpet and sound.

I have seen the panel in person but not worked with it yet.

I can say from a joint/seam perspective, this panel should beat any other panel on the market, bar none. none of the others have tubing shields above and overall the profile of any seams/joints are less than any other panel I've seen.

That said, I am not usually concerned with that, so don't take my statement as an endorsement, just an answer to your specific question.

It appears to be a decently engineered panel, though for slab retrofits I would tend to favor the Roth panel for its higher insulation value. That said, this one is definitely more "robust", not just being 60 psi EPS foam.