The central problem with DRM is that it stops only honest people. Anything that is located entirely on the user's computer in obfuscated form and plays from there can be cracked, and crackers will crack it, whereupon the cracked goods will quickly find themselves on BitTorrent and other sharing networks.
The thing is, competing with free isn't that hard. If you offer high-quality goods for a reasonable price, using an open format, at a convenient location, customers will buy from you. How did Tower Records thrive for so many years when recording tape-to-tape or record-to-tape was so easy? Or, for a modern example, look at Tor books, which has un-DRMed its books. They say the sky isn't falling. This transition has already largely completed in the realm of technical books at companies like O'Reilly, Manning, Apress, and others.
DRM is an endless and futile game for content creators, and an annoyance to customers. I doubt in the end that any DRM standard we settle upon will be sufficient for most publishers for many reasons, ranging from capabilities to safety, and in the end those publishers who are really serious about DRM will go with proprietary plugins anyway (and will find that those don't work very well either).