I only just worked this out, and have seen no other acknowledgment of this anywhere else.
I have 1x set of standard iPhone 3Gs headphones/mic + 1x in ear Apple headphones.
I have noticed that if you use headphones A and se the volume in the iPod etc etc, unplug it, and plug Headphones B in, change the volume to whatever you want, and unplug those. Each time you use either of those headphones, it actually remembers the last volume you had set (so each have their own volume level remembered).
This is actually really nifty for me, because at night, I use the standard headphones at a very very low volume, and during the day when working on the farm, I use the in-ear headphones at a higher-mid volume, so each time I plug in those headphones, I never (or very rarely depending on situation) have to change the volume.
Im curious to see if this works with other headphones? (I imagine that its Apple specific headphones however). Anyone else noticed this>