I think this is a great product.
IF u want to crank a machine and have others who are asleep or dont want to hear a loud machine, its a great idea.
BUT even if no one is around, i reckon with the headphones plugged in, you would probably hear alot of small things in the audio with more clarity than u would just by listening thru standard speakers. I notice on ALOT of pinballs, that you miss alot of audio noises unless u really crank the volume. For this reason alone, i reckon a set of this product is worthwhile. I reckon u could keep it portable as well and move it from machine to machine by not fitting it off permanently.
I will email n order one when they have them fully available n definately test it out 4 sure.