Timely BusinessWeek review of the Sansa/Yahoo!/ZING offering.
I'm still a fan of Yahoo! Music Unlimited, but my laptop is my primary music player at the moment, and I'm not thrilled with Yahoo!'s recent price increase...
Trying to beat the iPod at its own game has been a thankless strategy for makers of rival music players, who have barely made a dent in Apple's overwhelming market share. SanDisk, a company better known for computer memory than music, has wisely devised something different: a wireless player that downloads music on demand.
Source: A Better Wi-Fi Music Player