Microsoft is expected to unveil copy-protection software this summer that will 
for the first time give portable digital music players access to tunes rented via 
all-you-can-eat subscription services--a development that some industry 
executives believe will shake up the online music business. 

Microsoft’s iPod killer? | CNET News.com

We’ll see. Ingenous hackers have a habit of finding holes in security schemes, but it might be good for the masses.