RMS is closeMS is building up it's support for the launch of the Rights Management Server software later this year. RMS is a very interesting product - which solves some important security issues for many customers. The problem is how to protect information that is inside the firewall.
I remember many years ago reading an internal memo from a member of the Windows 2000 development team to the team. It was addressed as 'Dear Mary Jo' - since he knew that, within hours of being sent Mary Jo Foley would have a copy and would be putting spin on it in her column. At that time both she and Paul Thurrot sort of made a habit of posting internal information - stuff marked MS Confidential DO NOT COPY. I can feelfor Iain - it's tough to be honest in email where you need to discuss and evalute tough issues and come up with a good resolution, when you know your every word will be sent to people with very different motives (by people with very different motives!).
RMS enables you to create documents whose usage you can determine. You can, for example, make a document no print, no forward. The receipient can read the mail, but can't send it on (e.g. to Mary Jo), or print/fax it. Of course this won't stop analog attacks (taking a digital photograph of the screen, or simply re-typing all the text), but it will cut down on a heck of a lot of more casual abuse.
Right now there are only really two products that make use of RMS: Office 2003 and IE. With Office 2003, you'll need to have the Professional edition in order to create rights managed documents - you can view RM'd docs using Office 2003 Standard. But this will certainly change. I'd expect every native app that ships with Longhorn, for example, to be RMS capable. I look forward to seeing what innovations the ISV community has here! IE integration will provide security on documents provided via an Intranet solution. The IE stuff will ship separately. RMS, however, is not free. Take a look at the Windows Rights Management Services for Windows Server 2003 Pricing and Licensing Overview for the full license detail.
In summary, each RMS user (document creator and document reader) must have an RMS Cal (US$37.00 each). If you want external users to be able to access RMS software, an external Connector license is required: $18,066. So a 500 seat company will need to stump up in the region of US$50,000 for the CALs, the External Connector, and the RMS server - presumably this would be a new system requiring harware/software/services/backup/etc. Given the instant document security this gives you, the cost seems pretty reasonable, especially when seen in the light of of the cost of accidental disclosure.
Oh, and to get much use out of it just now, you'll need to upgrade to Office 2003. Maybe RMS is the killer reason for upgrading to Office 2003. I can see a huge number of firms who will love this and will rush to buy it. The IE component will be useful too, especially for firms with large intranet applications.