Lockergnome has a great article on why RSS is a superior to email publishing. [Thanks, PaidContent.org!] What’s great (and unusual) about the article is that it is written from the perspective of the user: here are ten reasons why your readers will demand that you make your newsletter available via RSS.
These advantages are indisputable. But RSS is not the best medium for communicating all messages. It’s great for headlines, but not for essays.
I don’t think this essay addresses the forces (e.g. inertia, the mental overhead of new software platforms, single interface for all communications) that will keep email vital for years to come.
The preferred strategy should be to give your customers a choice.