Adobe Framemaker
When I began using Framemaker, it was the industry-standard authoring tool for large publishing departments, and it was completely geared towards print and pdf output. This is still its primary strength, and it does the job beautifully. If you want to write a book of any kind, you use Frame.
Framemaker Templates
Success with Framemaker has always depended on understanding, and being able to work with, its templates. It's Frame's automated, template-driven workflow that allows authors to ensure that formatting will remain consistent as they work on a multi-chapter document; and allows publishers to ensure that branding efforts are enforced and consistent, from one document to the next, and from department to department.
XML Content
With the growing importance of digital content to all publishers, and the adoption by many industries of standards-based xml to allow more efficient communication between computers, Adobe was forced to adapt. It stuck a second, "structured," interface on the old workhorse, through which you can now write xml content.
(The old workhorse did not like this much, at first, and was apt to lie down on the job. Frame is a WYSIWYG editor. Its job had traditionally been to deliver good-looking, beautifully formatted documents. Now it was being asked to deliver plain, format-free, unadorned xml. I think it was affronted.)
Templates are still important, even when developing xml content, because they maintain the familiar WYSIWYG writing environment, and because they allow content to be saved as both xml and as a printable document.
The structured interface has added an extra layer of complexity to working with Framemaker but you don't have to use it. If you choose to, you'll likely find the additional benefits of creating xml content are well worth it.
Framemaker Creates DITA Content
Version 8, which I use, creates DITA content for print publishing very well. However, it needs third-party support to achieve DITA's full potential for electronic (online and .chm) output. As version 9 apparently handles this type of output much more efficiently, I am considering an upgrade. My purchasing budget and I are tussling over the issue as we speak.
Usage Matters
When did "writing" become "authoring"? Should the Plain English police intervene?
No. This is a case of vocabulary not evolving as fast as technology, and having to make do with what we have.
The "author" of a document is either: the individual or team that created the document, or the employer of that individual or team or, if the document was created under a "work-made-for-hire" agreement, the creator's client.
In the case of my own work with Adobe Framemaker, the task of "authoring" also includes non-writing activities such as creating and optimizing illustrations, copyediting, and graphic and book design.
Other XML Editors
If you're weighing the benefits of developing xml content, you should be aware that many, much more specialized, tools are now available.
Do a search on xml editors and see what comes back.
(And don't forget that xml is just text. You can always use Notepad ;-)