For me, it made an incredible difference.
I was getting acceptable, but not great, finishes on many of my prints, and spent about 30 hours trying to get a decent ironing profile sorted out. Never could succeed with any ironing settings that worked with HF nozzles, only standard (thread on Ironing reached the consensus that cooling was overpowerful and ruining the ironing lines), so I gave up.
Few days later, got my vision plate, ran the calibration test, and printed a box for a geocache. The surface finish of the inside feels like its ironed:
Its not the 100% glossy perfect my tuned X1C could get, but it’s consistent. The X1C would give you beautiful ironing, or it would choose to just spit out garbage, and there was no way to tell ahead of time.