Great with old-school Walkmans etc like my WMD6C above, but hopeless with an iPhone as modern kit tends to hate the 600 Ohm impedance. I was surprised by how easily the Walkman drives them when even my MacBook Pro struggles.
The latest MacBooks ((Pro and Max versions) supposedly have upgraded H/P stages which can drive high impedance (J Valour did a YouTube comparison recently).
I don't have a h/i headphone to test this though.