An SD card in your PDA will do the same thing as an Ipod.
Ipod is good DESIGN not technology. The Ipod is 100% marketing and packaging.
That said, COMPETITION IS GOOD!
You can't consider design as technology? The click wheel, the UI, the extremely tight packaging to achieve the small sizes? The iPod is where it is because it was the first mp3 player on the market that was really a consumer electronics device instead of a geek toy. Sure, others followed, but nobody's caught up yet.