serious user interface designers do, and anyone else who is anti-hype. the people that design cell phone interfaces go crazy with color and graphics, and it ends up looking like a TV commercial instead of a communications device. bigger screen? they use bigger fonts, rendering the higher resolution pointless. color capabilities? they use it to make everything cluttered and confusing with falling leaves and dolphin screensavers, instead of using color for its proper UI purpose - adding emphasis and differentiating one thing from another. hi-fi audio chip? they use it to make a ringtone that sounds like a chicken. lo-fi means less intrusive advertising and cheesy visual gimmicks - a text-based Internet was free of Flash ads, after all. i'll take my monochrome old-school Nokia over your Samsung media hell any day.
i'm not sure that a color screen would add much value to the iPod - it is a simple, primarily text-based interface that does really well for organizing text notes and showing music tag information. i would really like an iPod with digital camera connectivity, but it's not necessary to play back color photos on the screen.
keep in mind that other MP3 players have had color screens for years, and their battery life is upwards of 15 hours. granted, the players are much larger and use different batteries, but the impact of a color screen on battery life is overstated.