thanks for chiming in, sunfire. the handheld in question is actually a USB drive, read by my Sony car stereo deck. The deck is an xav-601BT, which is pretty well the most technologically advanced consumer-level deck out there in the sense that it has Mirrorlink (the touchscreen mirror's your android's screen) and its own OS is based on Android. The fact that even this deck does not intelligently handle multi-artist albums suggests to me that most car decks are like this (the one other one I tried with USB was the same). Aside from that, any old MP3 player I've used has had the same issue (though I'm not an iPhone/iPod person, and am happy to hear Apple's got that right).
so given this would probably be a relatively small amount of work for developers relative to how many people are affected, I think it's probably worthwhile. In the meantime, I've started using a separate MP3 tagger, which is less than ideal against the backdrop of MC-does-everything. As for your suggestion of using MC's existing tag&rename, the problem is, unless I am missing something, J River MC doesn't let you tag files outside of the library, which the handheld files are. I don't want to tag the source files in my library -- the whole point is to preserve track artist for multi-artist albums within the library, and only lose it on the handheld.
Cheers,
Shiraz